The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: nigeldtr on 13.06. 2009 17:57
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I have just bought a 1951 Golden Flash which runs very well and sounds fine. If I try to go above about 55 mph for any length of time (motorway or dual carriage way) the engine tightens up and stops - like someone quickly increasing pressure on the rear brake. When this happened, I quickly pulled in the clutch and coasted to a halt. I found that she turned over straight away and fired up and ran smoothly on tick over. No nasty consequencies (hopefully). This has happened twice now, still running fine but I obviously need to find the cause. She does not seem to be excessively hot and exhaust pipes are only a faint yellow. Oil seems to return to the oil tank with a good rate of flow which increases when I lift the engine revs - could it be lack of sufficient oil pressure?
Any tips or advice very welcome.
Nigel
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Does it coast along freely with a dead engine when you pull in the clutch If so, it the engine tightening.
You said you just bought it, has the engine just been rebuilt? If so, maybe you need to run it in more slowly until it has freed up a bit.
If you are fast on the clutch, can you keep the engine running, if so its the gearbox tightening up.
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Hello Andy,
Thanks for the quick reply. Had not thought of the gearbox as it felt like it was seizing however, the only two bikes I had that seized up on me both locked solid so you may well be right. When it happened, I was not quick enough to try the throttle so not sure on that. I'll take a look at the gearbox oil tough. I will also have a look at the pressure release valve do you know at what pressure thes should open?
Thanks Nigel
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Its pre-set, I think its about 55 or 60 PSI.
I dont think it will be that though or it would have seized solid and maybe thrown a conrod.
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Gearbox seizures are most uncommon, TR, and if they do occur, it's unlikely you'd ride away immediately thereafter. Most likely it's engine seizure, but check the gearbox oil level to be sure.
Query the seller to see about the bike's history. A recent rebuild - say, within a thousand miles - could mean piston seizure. Drain the sump through a coffee filter paper and see if there is any debris, especially aluminum. If no debris, things are probably OK; you'll just need to ride another few hundred miles at 50 mph or less (some back roads are always pleasant, yes?), drain the oil, and add a dollop of STP or engine assembly lube to the fresh oil. Bear in mind that the GF is not quite as well-cooled at speed as its alloy head successors. But remember, oil is cheaper than any BSA part in the engine. Change it early and change it often.
As for the oil pressure release valve (OPV), see BSA Service Sheet 203. It's function is to protect the con.rod big ends. There is no published value for its release pressure. In any case, it serves to lubricate the camshaft after the rods are deemed to have been satisfied pressure-wise. If the OPV spring is missing, is too weak or the ball therein is held off its seat by swarf or other means, then the cam is getting preferential oiling and the rods are suffering. In either case, the pistons are are being "fling"oiled as long as the oil pump is performing its job, which seems to be the case since oil return is noticeable.
David
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Nigel, if the engine has only just been rebuilt, it sounds like there may not be enough piston clearance.
Trev.
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Guys,
Thanks very much for all the info. Looking at the engine, it could well be that it has had a recent rebuild and is possibly a little too tight. I don't think she is getting too hot as the exhausts are the right colour and the motor is not "smoky" when standing. It does have a new Amal carb on it though (any tips on model and jets?). I will do an oil change and flush and treat as if it needs to be run in. This seems the most sensible approach, equally, I bought it to ride and not to strip down. All going well, I can wip the head and barrels off in the winter.
Not sure if it helped but I advanced the timing a little and added a little choke in the hope that if it was running to weak it would cool things down a little - does this help?
Lovely, old thing and I really am enjoying it - like being 17 again *smile*
Thanks
Nigel
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When I got my A10 on the road after a full rebuild.I was going along at about 50 mph one day when it started pinking badly and nipped up. I raised the carb needle 2 notches and it went much better all round (makes it run richer/cooler).After running-in was completed I think i lowered it 1 notch.Anyway,I havent had to adjust it in 6000 miles.
Might be worth trying.
Mike
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Hi Mike,
As I metioned, it has a new concentrc carb. I have not experienced any pinking but I think I will have a look and see if I can increase the fuel flow from the main jet. It could well be that at lower revs, the mix is OK but as I start to increase speed, it becomes to weak? If there are any other views or advice on the concentric carb, very welcome.
Nigel
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UPDATE - Just been out this afternoon and went for a slow ride through nice hilly country side. Had to use the throttle a bit between the gears nothing fast or hard but it was enough for it to tighten up again! This time she was deffinately a bit hot!! So possibly and overheating problem?
Nigel
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when I rebuilt my GF ( years ago ).. it had a similar problem... getting hot and slow & tight engine.. turned out to a be a tight timing side bush, if the bike has been recently rebuilt the builder could have made the same mistake I did I did not ream the bush to the correct tolerance, thought you just fitted it !! ( well I was just 18:-))..
you could wait for the real experts .. but I woulds be looking at the motor... something will exit stage right if your unlucky
ray
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Ray,
Is there any way to check this without stripping the engine?
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Nigel,
It does seem that the machine shop chose a very tight piston-to-bore tolerance. If so, you are not going to get over it until rings wear the bores or you pull the barrels and hone to a looser fit. If this were the small-end bush seizing the engine to a stop, your bush would now be history.
Apparenty, you have been able to restart when things cool off, so, no catastrophic damage, thus far. Earlier in this discussion, Dave (dpaddock) suggested the addition of STP oil treatment to make things slicker inside. Did you add that? Perhaps MolySlip E - http://www.molyslip.com/Products/MolySlipE.html - would be even slicker and would protect surfaces while loosening up. Having said this, I point out that I only know of the MolySlip products from this forum and have yet to try them (as far as I can tell, they are not marketed in the U.S.). I wonder if it would slip so well that the rings wouldn't wear the bores, as desired. Also, you must be sure that no oil moves from engine to primary case, as the MolySlip will kill a wet clutch and threaten a dry one if a bit of oil should cross the boundary.
It will be interesting to hear what others think of the MolySlip option.
Richard L.
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Richard,
Thanks for this, looks like time to take the head and barrels off! Last thing I wanted to do really but looks like the bores are a bit tight. Would love to think there is an easy solution but as with most things in life, I suspect not! Equally, each tightening I am sure puts a bit of extra strain on sometning somewhere. Many years ago I had a commando break a rod when it seized, made a terrible mess all over the road and cost a fortune to fix - almost new engine, never want to go through that experience again!
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Nigel... Love the comment...
Lovely, old thing and I really am enjoying it - like being 17 again
Thats exactly what its all about! Now personally I'd just stop worrying and carry on riding it, take it down to 40mph there is no rush I'm sure you'll agree, Change your oils very regularly and in no time you'll have covered enough miles to be able to go 50mph 60mph etc. I've found that these bikes Do need plenty of running time, once you've done that it'll run for many thousands of miles thereafter! Enjoy!
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Its only my opinion, but I wouldn't put any additive in the oil which would prevent the rings bedding in. If the rings don't bed in properly they "glaze" the bores, it will always be tight and will always use oil.
The sensible thing to do for a long term solution in my view is take the head and barrel off and check the ring gaps in the bores. Maybe the dude who rebuilt it forgot to "gap" the rings and when it heats up, it tightens.
If you haven't done this before, you take the rings off the piston and push them one at a time into their respective bore and push it down an inch or so with the piston to set the ring level in the bore, then check the end gap with a feeler gauge. You should have a gap of around 13 thou for the compression rings and 11 thou for the oil scraper.
If they are any tighter than that check the piston clearance you should have about 4 thou piston to bore clearance - if you have, its bored to the right size, so then you can set the ring gaps as above, you do this carefully with a smooth file on the end of the rings while held gently in the hand.
If there is too little piston bore clearance you will need to take the pistons and barrel to a re-borer and have them honed to size.
While its apart, look for seize marks on the pistons, if there aren't any, its not the pistons seizing - but it could still be the rings.
If you've never done anything like that before, I would recommend you get experienced assistance as the rings can break very easily.
If you already knew all that sorry this has turned into another epic.. I'm going for a lager.
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Hi Mike,
As I metioned, it has a new concentrc carb. I have not experienced any pinking but I think I will have a look and see if I can increase the fuel flow from the main jet. It could well be that at lower revs, the mix is OK but as I start to increase speed, it becomes to weak? If there are any other views or advice on the concentric carb, very welcome.
Nigel
Nigel,
My bike too was fitted with a new (monobloc) carb.But raising the needle cured the problem. It must be worth trying this before a strip-down.
Mike
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Andy, Mike,
Thanks for the reply. For my own peice of mind, I will probably have to take the head and barrels off as the memories of pistons scratching away in damaged bores is still all to fresh in my mind even after 30 years! Equally, I would probably never feel confident enough to open her up incase of the sudden, screech, bang and clatter of bits of metal skipping down the road in front of me as I slither to a halt!!
My big problem is time, I bought he A10 to ride and enjoy, not repair, so firstly I will see if I can return it and have a look for something else hopefully more usable. If this fails then I shall have to invest in some tools and try and find some time.
Thanks for the advice on the ring gaps and if I do take the top off, will I check these out - hope you enjoyed the beer!
Many thanks
Nigel
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I fully sympathise with your situation, it?s a b?stard when this sort of thing happens.
I hope adjusting the carb is all thats needed. Good luck.
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Andy, piston clearance depends on whether they are split skirt or solid. I wouldn't run solid pistons that tight.
Probably 4.5 - 5 thou.
Trev.
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I thought it looked a bit tight, those are the figures from the haynes Bible. Had a quick look in Roy Bacon but couldn't find it in there. I guess 4 thou would be good.
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Here is a extract from a BSA manual.
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Guys,
Just reading through the BSA instruction manual (Nov 1950) which came with my bike and to my delight it talks about rings and clearances - I wonder how many "modern" manufacturers would dare to do this, and it says, .010 to 015 for the upper rings and .009 to .013 for the scrapper ring - page 54 section 6.
Nothing like a bit of conflicting information to keep things lively *smile*
Regards
Nigel
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The service sheet that Brian posted shows the RGS clearance as .001" - .0025".
This is ridiculous for a solid skirt piston.
When I was a young bloke 30 odd years ago I had my RGS barrel bored to this clearance, after all it is in the factory book.
The engine did as Nigel's did, loss of power and tending to nip up.
When I finally pulled it down I had scuffed pistons as well as a tight bore. A fair bit of honing and polishing of the pistons and all was good.
Trev.
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I can't believe 0.001" sould have been spec'd for any aluminum piston split skirt or otherwise, in a cast iron cylinder. Coefficients of expansion are very different and I believe that was know before WWII.
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There are a couple of clearance recommendations in that list that are suspect if you look through it. When I did my 61' (iron head flash) top end I specified .0045". I used genuine BSA 8.5-1 solid skirt pistons and havent had a problem and I dont run my engines in, well maybe to the end of the street and back.
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If I can, I shall take the head and barrels off in the next couple of days and see what is going on. I strongly suspect that I wil have to do as you did Trev, have the bores honed out a bit and see if I can get away with cleaning up the pistons - bit if fine wet and dry I surpose?
I play a lot with steam engines and a driver once said to me, concerning a very clunky old loco, it is better to hear the bearings clunking then smell them!! (apparently they used to put some "stuff" around the bearings that when they got too hot, it melted and really stunk and could be smelt in the cab even at speed).
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That's a true story, they used Garlic oil.
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Nigel, when you get it apart, measure pistons and bore. If you don't have the equipment, get an engineering shop to do it. Probably a good ides to get them to hone the bore to correct clearance.
If your pistons have marks on them a fine abrasive paper should do the job.
Worst case will probably be grooves down the pistons and the piston skirts collapsed.
Mind you , this is if you have a tight bore. It could be something else entirely.
Trev.
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If I try to go above about 55 mph for any length of time (motorway or dual carriage way) the engine tightens up and stops - like someone quickly increasing pressure on the rear brake. When this happened, I quickly pulled in the clutch and coasted to a halt. I found that she turned over straight away and fired up and ran smoothly on tick over
The above is from the original post, I am no expert, but;
If the engine is "tightening up", like some one locking on the rear brake, then stops, then can be started straight away with no problems.
It is not consistent with too close engine tolerances, or any other mechanical part of the bike, for example if the rings were too tigh in the bore, it would have to take atleast 10 inutes for them to cool and subsequently contract to allow movement.
Sounds to me more like a fuel restriction or in the very distant possibilty a wiring/switch issue, I'd start with the carby and fuel lines, turn on both fuel taps, its quicker, easier and will cost very little.
If it was the magneto condensor it would probably take a while for it to cool.
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Josh, that is exactly what happens with too tight a bore.
Trev.
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Hi Trev,
Thanks for that.
I do not understand how the engine could stop due to rings being too tight, then the engine can be started straight away ?.
As stated I am no expert, but how does the engine instantly start working after stopping due to effectively ceasing, the ceasing force would have to be greater than say, 35 BHP, that is a considerable amount of force ?.
I am really interested in knowing the outcome of this issue.
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Without having experienced this lock-up my own self (thankfully), it would seem that the leap between the thinest possible film of oil, and no oil, is very small and the time for the pistons to contract the equivalent radius would be rather short. I think the engine stops quickly at the no-oil point, else, it seems we would not see so many scored pistons as, would they not be, melted, instead?
Richard L.
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When this happens the motor will usually restart almost immediately. I had it happen many times in my racing days and if you are quick enough you can pull in the clutch and coast for 50 yards or so and then let the clutch out and the motor will restart.
Unfortunately it almost always scores the piston and usually traps a ring or two in the piston. If it happens you have to pull the top off the motor and check it out. Most times the damage is very small and can be easily cleaned up. At the worst a set of rings and a hone and away you go.
Letting the motor work or labour is the worst thing you can do, revs dont harm anything. This is another reason to be wary of higher than standard gearing. Better to rev a bit higher than have the motor constantly under load.
I have told the story before but I bought my 51' A7 cheap because the previous owner didnt understand about gearing and kept seizing the motor and couldnt work out why.
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Well consider me educated, thanks gents.
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Just on Brian's revs and gearing point - couldn't agree more. Revs hurt nothing (though they can make unattended-to oil leaks worse). I run my A (standard iron motor) on one extra tooth on the g'box, and it pulls it just fine. But I also run a much revvier and low-torque 500 with an extra tooth . . . The next time the clutch is off, it's going back to standard. Just the few % difference is too much - too much throttle needed, not on the cams, poor fuel consumption and just generally not as nice as it was. Reason for doing it was to try to get a slightly more relaxed cruising pace on country roads, but it was a bad plan cos it didn't achieve it. No seizures though, luckily!
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Boring old bikes to too-close tolerance seems to be common. Apart from the strange info in the service sheets above, engineers are maybe used to modern water cooled cylinders.
I use "another well-known 650 twin" with 71mm bore and get good results from 5 thou skirt clearance on Hepolite and Taiwanese "Harris" pistons. Some original old pistons may have had different requirements.
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I think what causes this is a build up of excessive heat local to the rings, which is is due to high levels of friction.
As we know, when the rings heat up they try to expand but if there is no ring gap the closed ends push against each other and have nowhere to go, causing them to press excessive force onto the bore in turn causing excessive heat. This excessive heat is very local to the rings and piston surfaces, and when the engine stops, it only takes a few seconds for that heat to disperse releasing the force on the bores. The heat also atomises the oil locally compounding the problem.
Of course, this problem might not be that, but it looks very likely.
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i am a bit late in replying and have only read a few of the replies but I wanted to tell you that this is exactly what I experienced when I first purchased my super rocket, I duly treated it as new when I first got it keeping the speed on the low side for 500 miles and building up the speed gradually, during which time I increased the speed (revs) for short periods then reducing down to what I call running in speeds until I was happy that there was no noticeable problems.
When I went over 60 mph for any length of time the engine would start to tighten up and I pulled the clutch in before the engine actually seized, I then ran it in so to speak for a little longer but the same thing kept happening for any lengthy duration over 60mph, so after about the 5th time I took the bull by the horns and took the top end off, the pistons had tightened up in the bores and subsequently the rings grooves had pinched the rings.
I found out when apart that the pistons were 80 though oversize and had been supplied by SRM who also did the rebore now they reckoned that due to the make up of the pistons the clearance needed in the bore was less than BSA would recommend, I took the barrels along to our local BSA dealer (well he was in the 60,s and 70,s and is still trading) who measured them and declared them to be to tight a tolerance regardless of what SRM said. So after finding out that SRM had sold the remaining stock of 80 thou oversize pistons to MCA Hammond?s obtained a set from them and rehoned the bore to what they said was the correct tolerance, I duly fitted the parts back on rode it steady for a couple of hundred miles and have had no problem since, and ask any of the lads how I mistreat my super Rocket (70mph from Dover to Swindon continuously with only one stop and the last 6 miles between J15 to J16 M4 at 85 to 90mph)
So it would be worthwhile to take the top end of and check the pistons and bore even if for peace of mind.
Sorry for the book
Richard
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Trev,
Just finishing of a couple of "house" jobs and then I will bring her into the workshop - hopefully the next couple of days. Will keep you posted. I can't see it being anything else but we will see!
Regards
Nigel
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SRM who also did the rebore now they reckoned that due to the make up of the pistons the clearance needed in the bore was less than BSA would recommend,
So they bored it tighter than spec and it seized whenever it reached full temperature but it still wasn't their fault.
Glad you got it sorted!
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So they bored it tighter than spec and it seized whenever it reached full temperature but it still wasn't their fault.
TT
I do not see the reason behind your statement they did the rebore tighter than spec so if it was not down to them who's fault was it?
Richard
please do not read this wrong it has been written with a smile on my face and its not wind
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Don't want to interfere here Richard but I think there was maybe an ironic smile on TT's face when he typed also i am I right TT
All the best Bill
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Bill
Ahh I see what he means now its been a difficult day and the brain is a bit slow
Richard
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Sorry for being obscure. It was probably more sarcastic than ironic.
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Guys,
Well got the head and barrels off this evening and as suspected piston seizing on one side. The engine has obviously been rebuilt recently bottom end in lovely condition and cams also look good - may need new followers. To the main point - I have tried to measure the bores accurately as I can with good old analogue equipment and the good bore seems to be 2.817 and the "bad" one 2.814. Piston seems to be 2812, which seem to be a be too tight for comfort - or free running!
What a shame one lovely new piston and one scuffed up - looks like some time is needed with some wet and dry on the lathe and off to get the tight bore honed out a bit - I assume the pistons must be about +060.
Brian's descrition:
"When this happens the motor will usually restart almost immediately. I had it happen many times in my racing days and if you are quick enough you can pull in the clutch and coast for 50 yards or so and then let the clutch out and the motor will restart."
was spot on!! well done.
Back to the cam followers if I remeber correctly, these should have a nice round profile rather than triangular?
Thanks for all the feedback etc. great to read and follow.
Nigel
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Nigel
I am glad it is not to serious at least the cost should not be to much it is just a shame that the people who say they can do this sort of work do not take a bit more time and get it right the first time, as for the followers if they are not to worn they can be reprofiled as were the ones in my S/R.
I bought new ones for my gold flash and suprise suprise there was one follower that I had to rub down on a stone on one side to get it to operate without binding up, again the curse of pattern parts, given the choice I would rather have the original ones reprofiled which is what I intend to do with the ones I took out.
Anyway all the best
Richard
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I had my followers ground to the correct radius and had them heat treated to harden them.
Trev.
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Some pictures of the good and the bad!!
Out of interest, I popped a top compression ring into the bores and squared it up with the good piston and found that with the same ring the ring gap was 0.041on the good side and 0.031 on the bad side that would indicate the "smaller" bore is actually about .003 smaller. which seems to tie up with the measurements. Bad news is that it seems to me I have +050 ring in what should be +060 bores? What a shambles!
Will be taking all the bits over to a local company to measure up and hopefully repair. They said they can also reprofile the cam followers for me.
PS pitons are +060!
Regards
Nigel
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Nigel,
Wow! those followers are truly in bad shape. I will be interested to hear from Trev, or others, if the wear on yours is not, acutally, beyond refacing. Remember, everything taken off the follower face must be made up in the valve adjuster, which leads to further questions: Is there enough range in the adjuster screw to accommodate the change in follower length?; Even if there is enough range, does the angle of incidence between adjuster and valve become an issue? Considering you must still pay for the refacing, maybe GBP 93 for a new set from SRM is a good investment.
Now, considering the wear on the followers, what is the condition of the cam and other parts in the valve train?
With the piston scoring, I would not try to remove all traces of it. Rather, just take down the high spots. You probabaly don't want to adjust the piston fit by reducing the diameter of the piston. Instead, make the correction through honing.
Regarding the rings, doubtful you have a +50, as I don't think such were made. More likely a +60 improperly gapped. Get a new set to go with the rehoned cylinders. I have a set, but I'm not trying to hawk them here. I don't think you will have a hard time finding them all over the UK.
Regards,
Richard L.
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Nigel
When I saw the picture of the cam followers my first words out loud were Bl**dy H*ll I think I would agree with Manasound. My thought seeing the picture is why have they worn so badly or has someone done a hatchett job reprofiling them on a grinding wheel.
What is the camshaft like as surely with those cam followers some abnormal wear could have been caused to it.
£93 seems a lot to pay for cam followers even SRM ones, there are other sources in the uk that would have followers at less cost and possibly just as good, or look around for some genuine second hand ones that are better than those to be reprofiled if needed. More than likely there will be others like me that replaced perfectly good followers in the quest for a quiter motor only to find out it was not the followers rattling
All the best
Richard(Minety UK)
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When I lifted the barrels off, I looked at the camshaft and it seemed pretty good. At that time I had not seen the followers! Seems to me that the camshft was replaced recently along with the bottom end. Don't understand why the old followers are in there? The surfaces are a little scratched on the cams but not surprising considering the state of the followers. Anyway replacements will need to be found.
Are all rings the same? little concerned as the pistons seem to be "no name" and don't know if the grooves will match new rings etc - any exerpience here?
Nigel
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I have never had to buy just rings as when mine tightened up it pinched two of the rings in the grooves and although the pistons were not as badly scored as yours I bought new ones with rings (80thou) and decided to keep the old ones as good spares in the case of an emergency.
I since managed to remove the rings intact and then cleaned the ring groove out in the lathe. I would think that the pistons were machined to a standard as when people buy rings they try to get heppalite no matter what make of pistons they have so that would suggest that the rings are only in a standard width so to speak.
Richard
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I've no intention of setting myself up as the best expert on this, but the cam looks worn with scoring and also looks a little like the ends of the lobes might be wavy, which seems to be indicated by the three parallel lines of light across the lobe thats pointing upwards. Also, it does look a bit like the lobe ends are not even across the width of the lobes. If I could drag my fingernail across the scratches and get a noise, that seems like more scoring than one would like. On the other hand, it might just run fine for thousands of miles after the followers are replaced. It looks like there is oil in the gallery, so we might assume it was not running dry, at least, not recently. I won't be surprised if someone chimes in and tells me to stop waffling about the cam and just say it outright! OK, here goes, the best thing would be a new cam (maybe that's still waffling a little, but it's not my money and time).
In as much as you might easily justify a new cam (with the bike, not necessarily with your wife, if you have one), replacing it would give you the added advantange of being able to check all oiling paths including cleaning out the sludge trap. Someone less than totally careful worked on that engine. You don't necessarily have to assume that everythng is wrong, but checkng out the few things that can really sink you would be worthwhile.
Richard L.
As for the rings, if the pistons are made for an A10, I am rather certain that rings identified for an A10 will fit the width of the grooves. Your's look completely normal in that regard. If it truns out that they are gapped properly, you might just reuse them.
Richard L.
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For my two pen'orth that cam looks fine, they all have some kind of witness marks from use.
Unless of course you want perfection, if you do, I'll give you a couple of quid for the old one, but a new one would look like that after a few thousand miles.
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HI Nigel,
I hav just joined the forum, but am a longtime BSA owner, restorer/repairer
The root cause of your problems is the oil pump I rekon!!!
OK so heres my experience of this type of failure, (not on my bikes though *smile* *smile*)
1)low oil pressure due to bad, or porus pump body, worn timing side main bearing, or to tight bearing which has siezed on the shaft and the bush is turning in the steel sleeve!!
2) With low pressure the pressure relief valve does not open to bypass oil to fill the trough that the cam and followers run in. this leads to worn followers and eventually wrecked cam.
On BSA twins the first sign of problems is rattly tappets
3) Lack of pressure to the drive side big end, the rod should have a little bled hole in it facing up towards the piston, lack of oil leads to the left side piston siezing, then the rod breaks and wrecks the crankcases!!!
My advice to you is that you will have to strip the engine completely as there is now a lot of very nasty bits of cam follower in every concievable part of it, in oil tank, pipes and everywhere!!!!
A lot of owners complain about wet sumping on A7/10 engines, in my experience this is more often caused by the porus nature of the mazak (zinc alloy) that the pump body is made from
and or a little wear on the pump spindle which lets the oil leak past
anti syphon valves dont help here because the oil leaks out of the pump and then there is no prime in the pump to lift the anti syphon valve!!
My Super Rocket has modern pistons and runs at less than the original BSA specified clearance
and I have not had problems over 8000 miles,
I know an A10 owner who rebuilt his engine because the followers/cam were worn, new T/S main bush and bigends mains etc, it tightened after 50 miles or so but freed out again so he rode on, a couple of hundred miles later it blew up in a big way, breaking the drive side rod, holing the cases and wrecking the cylinder!
The cause of this was the oil pumb body was porus and the oil just leaked through the alloy, this is then picked up by the scavenge side of the pump and returned top the tank, showing normal oil circulation!
Apologies for being so long winded but there is an awful lot of mis information floating about
Regards
John O R
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Hello John, welcome to the forum.
My A10 had a really good return to the tank, despite the TS bush having 12 thou play when I stripped it, I think most of the oil pressure / flow was going out of the bush, its a good job its got a good pump.
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Hi Richard,
I have run my nail across the cam and although not perect, I will leave it in and buy new followers. I will probably do max 1000 miles a year and at the end of the day, I bought this to ride and not rebuild. Hopefully I can get her back together in the next couple of weeks and enjoy riding around the country lanes. Still need to get the battery charging - next action point!!
I have the tendancy of being a but of a perfectionist and if I take the engine out then I may as well repaint the frame, and the tin work and fix the crome, I am sure you know what I mean.
John, Thanks very much for your input here as you will see form the above notes, the bores are not right and running the good piston in the bores, there is actually a tight spot about halfway up on the side where it seized. If I have to strip the engine, I will never get it put back together as I have no time, so option is clean things up improve what I can and put her back together - I will have a close look at the oil pump etc and the piston oil holes in the conrods. If she throws a rod then you will probably see it on ebay for spares but lets hope it doesn't!!
I don't know much about suppliers being here in Germany, where can I get all the bits from?
Nigel
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In Austria, www.vintage-motorcycle.com
In Sweden, www.basmotor.se
In the Netherlands, http://www.petersclassicbikeparts.nl/index1.html (maybe)
Of course, many in UK:
www.draganfly.co.uk
www.srm-engineering.com
www.burtonbikebits.net
www.canddautos.co.uk
www.leighclassics.com
And the list, no doubt, goes on. I can't say I've heard of any in Germany, proper.
I understand what you mean about riding it rather than working on it, and removal from the frame is a much bigger commitment. It would be nice if oil could be forced through the crank such that you could watch it ultimately emerge from the tiny hole in the left rod. I think the how-to on that was covered here once, but I can't remember where or when. Checking or changing oil pumps is a much smaller commitment. However, I am having trouble envisioning enough porosity in the casting of the pump body to represent a leak, as suggested by John.
Richard L.
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Hi Richard,
Bingo! well I just tried holding the rods and pushing up and down and I managed to get the flywheel spinning and could see oil coming out of the oil hole!! so it coming through - what a relief. Obviously can't tell if this is enough but it is coming through.
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Hi again Nigel,
I did not believe that an oil pump could be porus either until I saw it with my own two eyes on a test rig!!
A quick check is to wash off the outside of the pump with some solvent, wait a while, minutes/hours and wipe the pump body with some tissue, you probably wont need to as you will see the oil on the metal
My Super Rocket wet sumped even though the pump had been overhauled and passed fit, because the oil leaked through the pump!!
For your own safety and peace of mind take off the timing cover and at least give the main bush a careful look at
Also remove the pressure relief valve and make sure its clean and operates properly,
IF THIS DOES NOT OPEN THEN NO OIL GETS TO THE CAM!!!! (and you r back to square one)
I know what you are saying about the bores, What make are the pistons?
Piston ring end gaps should be around 12/15 thou, did you have 40 or was it 0.40 mm
With a plain bush type crank engine it is possible to momentarily start the engine with the timing cover off to see whats going on regarding the pump and main bush
Regards
John O R
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Hello John,
Thanks for the coments and tips. Once I have the top back on, I will take off the timing cover and have a look and fire her up to see wha is happening. How can I check the pressure release valve?
RE the rings, the gaps I mentioned are in thou.
Nigel
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Hi Nigel,
Do you know anyone who works in industrial instrumentation, pressure testing services, or anyone who works in instrument calibration services
It can be tested on a dead weight tester or on a safety valve test setup,
The BSA relief valves use a ball bearing and spring , Triumph type ones have a piston, which can get stuck when shrapnel gets between piston and bore
You can mail pump and relief valve to SRM for testing if you like, testing is free if you have to buy a new pump (I think)
Regards
John O R
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Hi John,
I have a hydraulic tester here and can probably set something up to check it out I don't know at what pressure it should open and close at though - any ideas - perhaps I will give SRM a ring
Nigel
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Just for informtaiton, I spoke ot one of the guys at SRM and they said that the the pressure relif valve should lift off at 60 lbs and close between 30-40 lbs.
Regards
Nigel
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I'd test a relief valve by fitting a temporary oil pressure gauge to the bike.
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Nigel, get that scored piston measured, you will be lucky if it hasn't collapsed by the look of the grab marks.
For Richard and others who are interested in the performance of the reground cam followers, I have had no issues with them, everything seems to be normal. The ones I and a couple of mates had ground were worn but the grinding didn't take an excessive amount of metal. There are quite a few engines running with these followers and all seem OK.
Trev.
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Hi Trev,
Appreciate the comments. I have spun the piston up in the lathe and cleaned it up a bit. Some of the alloy had "dragged" and formed little hi-sptos which I have also taken off. As I have probably a 4 thou undersize bore, I can probably take a bit more off the piston and do some "fitting". I am not too happy about this as there may be hair line cracks etc etc, so I am considering buying new pistons and starting again. However, what concerns me a little more is, I heard that certain "new" pistons are prone to smoking and or seizing as the skirts are not turned with a fine taper (4 thou smaller under the rings than at the base of the skirt) to allow for the extra heat expansion at the top of piston. Whether this is only necessay with solid pistons or also applies to split skirt types, I don't know?
I have measured my "good" piston and taking the diameter above the gudgeon pin holes as zero reference, I found that the base of the piston, below the pins, to be approx +.005 bigger - OK holds to theory. However, do the same but at 90 degress, under the rings (below the "split") +.009 wider and at the base of the piston also +.009 wider, so would appear not to taper here!
So to sumarize:
Above Gudgeon pin "zero" same height turned through 90 dgress 9 thou wider
Base of skirt below pin + 5 thou, same height turned through 90 degress +9 thou wider
It would appear to my simple mind that they have turned the OD and then milled the split which means the stressed material "springs" I wonder if this- is common?
This really begs the question do I pay 150 pounds for a pair of pistons of questionable engineering quality or do I just do the fitting on the ones I have? If someone out there has perhaps a hepolite they can compare this would be great.
Thanks
Nigel
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Wiseco are making what they call "Rocket" pistons and these are / were available in the UK via cake street classics. Not sure about the other lower compression ratios.
Tel Roger Shirman on 01986 798504
Then of course there is-
J P Pistons Uk
The Glebe Keighley Road, Colne, Lancashire BB8 7HF
p: 01282864739 f: 01282864739
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Hi Nigel,
The measurements you have taken on the good piston seem OK,
Pistons generally are tapered, but they are oval as well, then they are stepped down in diamater between the rings nearing the crown.
In general terms the only relavent measurement that needs to be taken is at 90 degrees to the pin at the Bottom of the skirt,
This measurement should be the nominal bore size less the piston clearance, ie, 71mm minus 0.1mm(0.004in) for example
Stick the piston in the bore in the running orientation and an accurate measurement can be done with a feeler gauge.
With split skirt pistons the clearance is normally smaller than solid skirt, that said my Ariel 500 single 81.8mm bore has a split skirt piston and runs on 0.001-0.003in. clearance
My Super Rocket with solid skirt pistons is running fine with 0.003in (GPM pistons)
If you buy new pistons, the bore size will be marked on the box, not the piston size if you follow me, so have your engine shop finish the bore to that size.
Nigel You will have to believe Me and start looking at the oiling system in your bike ( I know the bore sizes appear or are different)
But the fact that the cam followers wore so badly and then its the left hand piston that siezed makes me very sure thats there is an underlying lubrication problem.
Triton Thrasher, its not an easy thing to attach an oil pressure gauge to an A7/10 engine, neccitating drilling into the crankcase to the oilway inside the pressure relief valve, its a bit easier on SRM type end fed conversion engines, by drilling in to access the end of the pressed in oil pipe, or into the outer cover
Regards
John O R
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Triton Thrasher, its not an easy thing to attach an oil pressure gauge to an A7/10 engine, neccitating drilling into the crankcase to the oilway inside the pressure relief valve, its a bit easier on SRM type end fed conversion engines, by drilling in to access the end of the pressed in oil pipe, or into the outer cover
Interesting, thanks. Can one drill and tap into the dome of the relief valve, for a gauge takeoff? Not that I'm that keen on oil gauges, but the guy wanted a test for the operation of the valve.
Edit- that's silly isn't it! You'd only be measuring pressure in bypassed oil.
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This really begs the question do I pay 150 pounds for a pair of pistons of questionable engineering quality or do I just do the fitting on the ones I have? If someone out there has perhaps a hepolite they can compare this would be great.
Thanks
Nigel
Nigel.
If you are going to buy new pistons ,heres my .02p,s worth.
SRM bored and supplied pistons for my A10 .Unfortunately i dont know the make but they are new pattern parts . They are solid skirt .I have done nearly 7000 miles and my engine goes fine and does not appear appear to burn any oil.
Mike
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Only my opinion, but a new piston of the type you have on the other side, or a pair of new pistons, is a better bet than prettying up and resizing that scored seized mess.
Buy from a seller you trust. There are good Taiwanese pistons.
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Guys,
Thanks very much for all the valuable comments. I have popped in the good piston in and in the RH bore roughly 5 thou clearance LH bore approx 3 thou, so is a little tighter. I will get the bores sorted out and pop in a set of new pistons. Are they normally solid skirt for a 1951 GF or does it make no difference?
I have taken the timming cover off and cleaned the outer of the oil pump, I will take a look in the morning. There is oil building up in the sum so its leaking back somewhere! I have tried to move the crankshaft up and down but there seems to be no play or very little in the main bearing (also tried pulling up and down on the rods but nothing noticable. Is this sufficient to check the main bearings?
Must admit I am seriously tempted to fit a new oil pump and pressure relief valve, will perhaps send the old ones off to SRM to be tested.
PS the dynamo chain area was absolutely stuffed full of grease never seen so much, hardly any room for the chain!
Thanks Nigel
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I've often wondered, how come the dynamo chain area is stuffed full of grease, but there is never any on the chain? *conf*
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Nigel, I feel that if there was anything wrong with your oiling system, you would be replacing big end bearings and grinding your crank.
As I said before, your case is typical of a too close piston/cylinder clearance.
The cam followers are worn and most likely were not serviced on the last tear down. Hopefully the sludge trap was cleaned.
Originally the Flash would have had split skirt pistons which run at closer clearance and should make the engine run quieter.
Solid skirt pistons are OK as long as you have the correct clearance, which you didn't on one side.
If you are worried about your oil pump, strip it and have a good look at it. Strip the relief valve and ensure the ball and seat are in good condition and replace the spring if you are concerned about it.
Oil is probably leaking past the check valve behind the oil pump. It is a major job to access it.
Trev.
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Not that I expect the decision to be made on my opinion, alone, but I don't see the immutable necessity of replacing the pistons. Maybe I'm too cheap, or, maybe pistons are just getting too hard to get.
If it were I, I would emory the scuffed piston until the high spots were worked down, measuring as I go to be sure the diameter and ovality stay within spec. If there is a lathe available, wrapping the emory around a wide flat file and moving about evenly(and gently)should avoid ruining the profile. From what I am seeing, there is at least as much unscuffed surface as scuffed. Then, I would hone the cylinder myself with a common cylinder hone until the fit of the scuffed piston was correct.
If you do happen to go the new pistons and professional shop route, get the pistons and new rings first, so both can go with the barrels to the shop. I say this because of your statement "I will get the bores sorted out and pop in a set of new pistons."
As we say around here, just my 2p worth.
Richard L.
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Well, I have manged to clean up the piston in the lathe and to be honest it looked far worse that it actually is, there are a few scores but his tends to happen in time anyway. I tend to agree about the pump, I had an oil pipe blockage on a B40 and at first I heard it start to rattle then in locked up. Result was shot main bearing, big end and piston. As the big end on the LHS is good (where the seized piston was), I suspect the piston is getting enough oil. The piston looked like it hard 3 - 4 pinch spots which would to me indcate it is just too tight.
I will buy a hone, get some new rings and do a bit of fitting. I can give it out to be done but heck I may as well have a go seems I probably can't make a worse job. will drop some more pictures on later.
Just had another look at the oil pump. The body does not seem to be porous but there is a slight leak aroud the joint where the drive extension is. Will strip and give it some TLC!
Thanks
Nigel
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I've often wondered, how come the dynamo chain area is stuffed full of grease, but there is never any on the chain?
This is because the wrong grade of grease is in there.
It should be a low melt grease so that under operating temperatures it melts and lubricates the chain.
IF high melt grease is used the chain picks it up and throws it to the extreamities of the enclosure and eventually runs dry.
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Trevor,
Seems logical, at bit like the tea lights, liquid when hot a hard when cool. Do you know if there is any particular make or grading for this?
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Well because I am an Aussie and we got a lot of sheep down here I use Lanotec which is a lanolin based grease.
I also use it liberally on electrical contacts as that was its original use so it is oft called "contacts grease"
Bought a big tub of it years ago and will probably never buy another as I have switched to "liquid Electrical tape" to water proof all of the places where the Lucas smoke gets out.
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Hello All,
Well, finally got some time and bits are now starting to arrive so on with sorting the A10 out!! I bought myself a hone and old MZ bike cylinder to practice on and then gave the A10 clyinder the works this evening. After a couple of hours of measuring cleaning honing etc etc finally got both cylinders almost exactly the same size! In the end I used a 4 thou brass strip to check that both pistons moved with the same effort in the bores. To double check, I popped the same top ring into the bores to check the gap. One bore has a gap of 15 thou the other 12 so one side is probably 1 thou bigger. As the gap is recommended between 10 and 15 thou, I will leave things as they are, measuring plus or minus 1 thou is a bit beyond me and my fingers :-)
Next tricky job is to drill through the crankcase into the bottom end of oil pressure release valve housing so that I can fit an external pressure gauge - I want to see what is going on in there!
Regards
Nigel
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All,
Just wanted to say thanks for all the helpful advices and tips finally got the engine fired up tonight and running nice and sweet. With all the discussion about oil pressure, I decided to drill trough the crankcase and pick up the oil pressure before the release valve, I have now fitted a pressure gauge near the top york and can see it from the riding position. Already been useful as it took ages for the return to pick up the oil and the engine almost filled with oil before it started to return to the tank (had to drain the sump as it started to come out the breather). I was not too worried as I had a good 20 to 30 PSi on the gauge with no oil returning! At tick over it shows 10 psi and when the revs are lifted goes up to about 30 psi - nice and reassuring.
Now just need to run her in!!
PS I found a company that supplies a liquid grease!! ideal for the dynamo chain drive, is like a jelly when cold and becomes liquid when warm.
Regards
Nigel
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Nigel,
Congratulations on getting her back together and running again. There is a certain reward in riding the bike one has fixed oneself.
One thing, I don't think you ever told us what you did about the followers. I assume, replaced.
Richard L.
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I don't want to hi-jack this important thread but I just noticed back in June by Trevinoz it was posted that there is a check valve behind the oil pump which can be the cause of wet sumping but is hard to access. I heard someone locally say once that with an SRM conversion (pump?) access to it is easier. Can someone clarify this hidden check valve situation for me please? The reason I ask is that I have recently bought an A10 which had a holed piston before I bought it and the owner may well have not thoroughly cleaned the debris out of the engine (as well as a subsequent seizure!, which is why I read this thread) which actually now severely wet sumps. I intend to strip the engine right down so any advice on this check valve would be appreciated. Thanks.
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Hello Richard,
I decided to change the followers and leave the cam alone. I could not find any convincing reason reason for replacing it. While I had everything stripped, I serviced the mag and the dynamo. The nervi bit was honing out the undersize bore which I did until both pistons moved freely as described earlier. The pistons where cleaned up in the lathe with some fine wet and dry and new rings fitted (the old/new rings were way undersize with too big a gap!). One lesson I have learnt is never take it for granted that a cylinder has been bored correctly (check it) and secondly, that pistons and rings can simply be taken out of the box, popped in and forgotten. It is time well invested to ensure that all the tolerances are correct and that everything fits and moves freely.
The oil pressure gauge is nice to have and when first started, the pressure shoots up to around 40/50 psi and then drops back to about 30 when warm. I am now seriously thinking about putting an oil filter in the return line as there is plenty of room behind the gearbox. It was a joy to fire her up and the sound is what dreams are made of.
Alan,
Concerning the wet sumping, my A10 was slowly draining down the oil tank all by itself while in the workshop. In normal daily or weekly operation, I can't see this ever being a big problem, just fire her up once a week. Alternatively, drain the oil out and top up with new - one way to keep the oil fresh. How much oil is actually flowing back into the sump ? how fast?
Do you know why it had a holed Piston ? was it mechanical failure (valve problems) or did the crown melt?
Nigel
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Hi Nigel,
30psi is not enough to operate the pressure relief valve, this is Very Necessary to keep oil to the camshaft and followers, going back through the replys you got from your initial problems there are figures for the valve!
When you started the engine, the sump should not have filled with oil!
The scavenge (return) side of the pump has a greater capacity than the pressure side, and it will in normal conditions will clear the sump faster than it can fill!
As I have said to you in previous replys I feel very strongly that there is a serious problem with your lubrication system????????
Alanp,
After an engine holes a piston the debris gets absolutely everywhere!!! (and amazingly quickly)
You will have to completely strip the engine also the oil pump,
clean out the crank sludge trap, oil pipes and tank as well!
I have used aerosol brake and clutch cleaner with a long nozzle to clean out the oilway to the cam gallery
You can remove the plug for the valve from inside the crank case,
Its up to you if you replace it in the same way or modify to the SRM (A65) type setup where the ball sits against the back of the pump
Regards
John O R
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John,
I can't remember but is the camshaft only fed when the pressure release valve opens? The engine does not wet sump any more, it took while for the scavange to pick up and now it returns fine. Have you or anyone else fitted a pressure gauge as it would be good to know what others have found. I can change out the pump, I think Draganfly do a reconditioned unti for about 100 pounds.
Thanks
Nigel
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is the camshaft only fed when the pressure release valve opens
opposite, valve redirects whatever is left after crank gets it's oil dose.
Nice pressure gauge mod, just some quick thoughts, you are reading the pressure after feeding the crank and may get a quite low reading, still everything will be ok (or plain bearing is very worn and leaking direct to crankcase, if you get a very high reading I'd think maybe the big ends\plain bearing are not fed properly!) Corrections welcome.
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John,
I did a little digging and just found the attached showing as you say the oil feed to the camshaft. I am going to take out the pressure release valve again and check the operating pressure. If the pump is not opening it then I will replace the pump.
Thanks for the tip - reminder!
Nigel
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is the camshaft only fed when the pressure release valve opens
opposite, valve redirects whatever is left after crank gets it's oil dose.
Nice pressure gauge mod, just some quick thoughts, you are reading the pressure after feeding the crank and may get a very low reading, still everything will be ok (or plain bearing is very worn and leaking, if you get a very high reading I'd think the big ends\plain bearing are not fed properly!)
Hi and thanks for the comments.
The pressure take off is below the release valve so in theory, this should be the same pressure as at the main bearing and is really the pressure acting on the release ball. All depends on what pressure the release valve opens. Which I will find out tomorrow. I have not really lifted the revs yet, so prehaps the pressure will increase when I take her for a run. All interesting stuff!
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Hi John,
I have just carried out a few tests and found that by lifting the revs the pressure went up to 50 psi and then held there. This seems to be where the relief valve is opening. To double check, I slackened off the release valve spring retaining nut and could lower the opening point down to 40 and 30 psi. When tight it is operating at 50 psi. From these results, the pump seems to be doing its job. I will check it again once I get out on the road and can see what the pressure it stabalises at.
Nigel
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Hi Nigel,
That sounds Better!!
Let us know how the road testing goes
In the photo of the cylinder and piston you have the brass feeler (shim) measuring the clearance at the top of the piston (or is going all the way down??)
Clearance should be measured at the bottom of the piston at 90 degrees from the pin
Cheers
JohnO R
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John - really appreciate the feedback!
so, running on SAE 40 the engine starts and goes upto about 50 psi when the revs are lifted a little from tickover (relief valve opening). Once the bike has been driven for about 10 mins and she is getting hot, the pressure slowly falls away as the viscosity drops, infact gets down to about 20 psi at which point the release valve will never lift and send oil to the camshaft. After the initial start, I assume there is plenty of oil in the trough to keep things lubricated at least for a while - untl the next cool start? I live in German and it is currently about 30C so I am going to change to SAE 50 and see how we get on. I have no issue about buying a new oil pump (or perhaps better an oil cooler?)*smile* however, I suspect that even with a new pump, the oil pressure when the engine is hot never gets high enough to open the relief valve?
I appreciate a high capacity pump will shift more oil and perhaps improve the pressure but do you or does anyone else know what the"hot" runnning pressure should be (I assume greater than 50 psi to open the relief valve, however, for a hot, journal bearing engine, this figure seems impossible?).
Regards
Nigel
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In the photo of the cylinder and piston you have the brass feeler (shim) measuring the clearance at the top of the piston (or is going all the way down??)
John, the shim went all the way down the bore and was at 90 degrees to the pin. The seized side took a lot of work as there was a high spot half way down! In the end, both bores were a nice sliding - push fit.
Regards
Nigel
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Hi Nigel,
It looks as if there is either wear in the engine plain bearings or in the oil pump,
or a combination of both???
My Fathers old grey Ferguson behaved like your BSA!! 0 psi when the engine was hot *sad2* *sad2*
You could try running the engine for a little while, with the timing cover removed when hot
you should be able to see if the oil pump is leaking (a lot??)
This is a messy test!!!!!!
There are a couple of suppliers of either iron or alloy bodied pumps
Another issue can be if either the fibre washer under the front mounting screw is either missing or too thick!!
What I do is make a gasket like an A65 one that extends forward to include the front screw.
have a look at this as well. http://www.srm-engineering.com/technical/wet-sumping-problems
Dont complain too much about 30 degree temps!!!
It looks like winter is on the way here in Ireland!!! after we have had the wettest summer on record!!!!!
Regards
John O R
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Weather-wise, Chaterlea is right. However, what the Atlantic clouds don't drop on Ireland it off loads the rest on SW Devon. That's why we're both green but fed up! Roll on next riding season, it can't be worse.
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The weather was part of the reason for me moving from Manchester to central Germany - the only problem is that it is often too hot to go out *smile*.
Re the SRM info, I will have a closer at look but I note the tests we done at 21 C with 20 WT oil not really engine temperature or recomended oil? I would also love to know how and what, the pressure drop test and the "running" tests where tested against, a valve which was openened to give a restriction at 50 psi then closed for the drop test? If I get time, I will give them a call and ask.
Tomorrow I will pop in the SAE 50 and do some more testing.
PS don't doubt that their pump is super, I like comparisions to be more "lifelike" though perhaps there would be no difference?
Regards
Nigel
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I swapped the oil for SAE 50 and found the relief valve opening almost as soon as the engine started ie just above tick over (tick over showed 40 psi). However after about 10 mins running, the pressure slowly started to fall and final held at 10 to15 psi for the the rest of the run.
I spoke to the guys at SRM and they explained the test process and seems perfectly valid running on a ?thin? oil to show up the weakness. After a good discussion, it seems that in anything but a new engine, the oil pressure will not be high enough to open the relief valve once the oil gets hot hmm!
Ok, a lot is dependent on the main bearing wear otherwise oil rushes out here and drops the pressure however, any engine with a bit of wear will not be oil tight here! It seems that the camshaft gets it dose of oil when the engine starts from cold or cool, and this is topped up from the rocker oil running down. If this is the case then long runs, like motorways etc are the death of the camshaft? Seems that a leasurely run with a few stops to let the oil cool and then set off again is the best ? I think this known anyway *smile*
I would love to have some other comparisons with others with oil gauges but this seems to be a little rare!
Nigel
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There must be a minimum hot oil pressure quoted for your bike. I don't have a manual to hand, but it will not (surely?) be 15psi at road speeds!
I'd say you have worn bearings: main bush, big ends or both.
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Hi Nigel,
Looks like the next step is as I suggested, a short run of the engine with the timing cover off (when hot)
to see how much oil is passing (leaking) at the pump
Remember what I said about the fibre washer!!
It would certainly be a first step before a complete engine strip
Regards
John O R
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Well, I am am now coming to the conclusion that the main bearing is worn and dropping the pressure or pump is too weak or leaky. When I had the barrels off, I checked the big ends and they are fine. I tried to move the crank in the main bearing but at the time could see no excessive play. I took the timing cover off and fired her up but with rush of air from the crankcase I could not really see where the oil, running around, was coming from.
For info, I was out today for a short while and measured the oil temperature as the pressure dropped. At start, high oil pressure and release valve is opening (the return pressure is so high that it actually causes a few leaks around the rocker spindles).
Air temp today 20C, so ideal for the engine and rider.
Oil straight SAE 50.
Over 55/60 psi at 18C (cold engine)
35psi ? 40C
20 psi ? 50C
15 psi ? 55C
12 psi ? 60 C
10 psi ? 65 C ? no further reduction after this.
To me the oil temp seems fine but the pressure drop is a real pain. From what I can see from the viscosity charts, a 3 fold increase in temperature (from 20 to 60) brings about 10 fold drop in viscosity! So with lower viscosity I need to move a heck of a lot more oil. So the problem could be pump capacity or shot main bearing leaking too much.
The next step is to remove the pump strip and check and also check the main bearing for wear and then have another scratch of the head ? I'll keep you posted.
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Had a spare hour so took off the timing cover and pump! The main is worn and will need replacing at some time (not before winter). From looking at the pump, the engine has failed at some time and dragged debris into the return and feed of the pump. The feed side being particularly badly scored. I have attached pictures. Also looks like the wood worm have been at the body as there are plenty of holes around in the casting - for you John, I thought you would like these re your earlier comments. I will order a new pump Monday. I will flush out all the oil ways and oil tank and fit an oil filter, would prefer to put it in the feed side though to protect the pump. I presume it would have to be primed to ensure it flows freely.
Pics 2 and 3 feed, 5 and 6 return.
Nigel
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That is interesting stuff and, obviously, very revealing. I would like to hear from John if that is the kind of porosity he had in mind. Those "wood worm" holes look like they could be the result of corrosion. I am looking forward to this new bit of knowledge.
Richard L.
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i see thats a case ove irish woodworm *smile* at least youve
found somthing
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This is one of the best and most informative set of postings yet! Thanks to all for your inputs.
Two comments:
- add a dollop of STP to the oil to restore lubricity to our "modern" formulations (which have fewer of those additives in order to keep automotive catalytic converters from dying prematurely). This will help preserve cam and follower surfaces (an important issue since A7/A10 followers cannot rotate);
- the drive side crank journal is the last item lubricated before the oil is flung off to lubricate the LH cylinder bore. This is why the LH crank journal, rod bearing and piston almost always appear distressed compared with the RH. In racing extremes, the LH side gives up the ghost first. This is the major reason why it's so important to change oil frequently - and to ensure the sludge trap is clear.
David
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Hi Nigel and All,
I have seen holes in the castings like you have, normally no problem unless they go go right through *ex* *ex* *ex*
Its the scoring in your pump that has it wrecked, remember its now at least 60 odd years old!!
The porus pump bodies I have come across look bad from the outside, the alloy (??) looks crappy and crumbly
The new pumps use A65 gears which are wider so you get more oil circulating
Apparently when BSA closed there were tens of thousands of oil pump gears left surplus
These are now being used for the new pumps
Nigel, fitting an oil filter on the pressure side of the system should be after the pump, it can be done if an SRM type conversion is done!
There should be NO restriction in the feed from the tank to the pump
If you clean out the tank properly there will be clean oil for the engine
I have a filter in the return line so the return oil to the tank is always clean, I also put a magnetic drain plug on the tank and a magnetic plug in the sump plate as well!
After a couple of oil changes on the rebuilt engine it now doesnt have any crud on the magnets and the tank stays really clean!!
HTH
Cheers
John O R
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Why is everyone getting so excited about oil pressure? The reason pressure gauges were removed from motorcycles was precisely because what is happening here.
If you look at the late model bikes with oil warning lights, you will find the switch is set at something like 7 P.S.I.
It is probably more important to have high volume than high pressure.
By all means replace badly scored housings and worn gears as gear pumps rely on minimal clearances to maintain supply.
I have been involved with A engines for more than forty years and have not had one fail due to oil problems.
I always strip and inspect the pump and then test it by submerging it in oil and driving it to ensure it is working.
I strip the pressure relief valve and ensure the ball and seat are in good nick, I have found some with really bad seats.
Replace the spring if necessary.
I have had a failure exactly the same as the start of this subject which was due to the machinist boring the barrel too tight.
If you disagree with me, please don't abuse me.
Trev.
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Hi all,
firstly, thanks for the replies really useful. A couple of weeks ago, I spoke to a specialist oil supplier for classic vehicles and started of with SAE 40. However, with about 30C ambient temperature the bike warmed up quickly and the oil got very thin ? difficult to fine more 5 psi when hot, hence the switch to SAE 50. The only problem is, the thicker the oil the slower it gets where it is needed and initially does not flow around well enough. Ideally we need good pressure and high volume lower viscosity, gets everywhere, lubricates and cools! As the engine wears, oil pressure drops etc and pressure is still important to keep the bearing faces apart under load. The oil supplier said I should be pleased with 5 to 10 psi as the pressure at the big ends, due to the centrifugal forces, will be really high (provided oil ways are not blocked!) and without pushing the engine hard, the crank will hopefully be ?floating? in the main bearing.
Now the real drive for all this investigation ? as discussed from earlier, not only did my piston seize, but the cam followers where shot. If the camshaft only gets its feed when the release valve opens, then we need oil pressure! I feel sure that the only time the valve opens is when the engine is either new, has no leaky bearings, or the oil is cold and thick. To me you would need a very high pressure/volume oil pump to have this especially with an operating oil temperature of say 70C on an SAE 30 oil. As mentioned in the discussions, I suspect that the oil trough fills when the engine is cold or cooled and is topped up from the oil running down from the rocker box when at normal running temperature.
Forming conclusions
When putting the engine back together, I also checked the timing and noticed it was way too advanced. My conclusion is that the seizure was due to 1. a tight bore and 2. over heating due to the extremely high combustion temperatures. The last time I ran before the strip, I did notice it was a bit oily smokey around the barrels and head. At the time, thought nothing of it, just a hot day +30C but in hindsight, this was probably a warning indicating the timing was wrong and she was about to seize on me. More oil may have helped to cool things down but I doubt that it would have made the difference.
I would love to see the pressure about 20 psi on a SAE 30 or 40, which would give me good flow, and cooling. Once I have a new pump, I will test again and see how we get on.
PS as the oil I am using has no additives, I will definitely pop in some molyslip or similar once I am run in ? hopefully I get that far this year. As new sump with magnet has picked up plenty of muck. Look forward to getting a filter inline!
John, where did you get the filter from?
Nigel
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Hii Nigel,
I am against using extra additives in the oil, your supplier probably meant that it was detergent free, all engine oil has additives, its a long way away from what comes out of the ground!!!
I have seen additives block screen filters, its so gooey it wont flow through them, *eek* *eek*
Back in the 70's/80's I had to repair a lot of BMC minis /1100's that wrecked the transfer gear/bearings from the crank to the gearbox, every one of them had had STP/Molyslip type additives added to the oil!!!
The additives coat the neele roller bearings and reduce the clearance in the bearings, then they over heat and fail
Attached is a pic of the filter setup on my SR, I am using a Norton commando type filter head, I think I bought it from Bri tie, anyway they are commonly available.
I fitted this in the toolbox with the pipe connection stubs protruding through the rear of the toolbox
These heads have a 16mm filter thread, not too common nowadays,
In the pic you can see me holding a threaded brass bush
this is a 16/20mm electrical conduit adaptor
I had to bore out a couple of threads at the nut end and then it screws on over the 16mm stub on the housing
Now I can use a much smaller filter available at any motor factors!! (And cheaper to boot!)
It also leaves me with a useful amount of space left in the toolbox,
I have mounted my Podronic regulator under the seat
HTH
Regards
John O R
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Well pump, drive, filter and other bits all arrived today ? super service from Draganfly! I have taken the oil tank off to give it a clean but what is the best way of getting rid of the sludge in the bottom?
John, thanks for persisting on the pump front, a painful but necessary investment!
Nigel
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I use a petrol paraffin mix, blank everything off & do the old Tom cruise "Cocktail" shake, as many times as needed , then blow it out with an airline.
Others use a pressure washer, if you go that route definately use & airline to rid residual moisture & cook in the oven.
Cheers
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Others use a pressure washer, if you go that route definitely use & airline to rid residual moisture & cook in the oven.
That's a *good* tip... I've not thought to do that after pressuring!
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A trace of water in the oil tank isn't the end of the World. In normal service some water always gets into the oil. I clean tanks with petrol, kerosene or similar as available and then with hot water and detergent, rinsing with hot water. I shake out the water and put something oily in the tank to stop the rust forming.
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Thank you for all the tips re the tank cleaning. Gave it a bit of everything and even put in a box of small nuts to knock off any loose bits makes quite a good maraca!! Dried it out by resting a hot air gun in the filler end and leaving for a few minutes.
Just managed to fit the oil filter and do the pipe work - what a pig of a job, my fingers are in shreds. Tomorrow all the bits will be taken off again, given another good clean then put back together and hopefully fired up.
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Well finally got the GF fired up this evening and running fine. SRM pump fitted and oil filter in the return. Took her out for a run and once warm the oil pressure sits at a good 20 to 30 psi which is double that prior to the new pump. Considering the timing side main bearing is very worn, this is for me is a good result and I can get a few gentle miles in before stripping to replace the main.
I am sure you know how its is, hours of work wasted and feeling rotten about unfinished work and problems, well thats how it was at lunch time. It took me ages to get the filter pipework sorted out and to make a suitable bracket to mount the filter on. With this done, I then went to do the enjoyable bit ? fit my new oil pump! Well unpacked a very nice looking pump, grabed the new worm, lockwasher and new locknut (did not want to reuse the old ones looked a bit worn). Primed all the oil ways, offered up the new pump and worm and bingo, found that the new worm wound not start on the thread properly too tight. Took it off, and tried the new lock nut, the same, both where too tight on the crank threads. Having screwed up many good threads in this manor I immediately, put the new ones to one side and refitted the old ones (not happy about this, another half fix). O well, lets finish this off now, I thought, put it all back together, kicked her over several times without the plugs in to make sure oil came through to the release valve, fine. Ready to fire her up, now the real fun started, along with the engine!
While I was listening to the wonderful exhaust note and dreaming of the open road, as I waited for the oil to return to the oil tank, I suddenly heard what was a sort of soft "pop" and oil went everywhere. The sealing rubber ring at the top of the filter had blown out the side and what a mess, all over the drive. Well, clean up and try again, but tighten the filter properly this time. With a lovely clean bike, soiled drive and tight oil filter, I fired her up again and yuup "pop" it went again, even more oil on me the bike and the drive! Well time to scratch my head and wipe the oil off my face. Well perhaps SAE 50 is too thick for the filter and the new oil pump too good, hate to think what the pressure in the return pipe must have been! O well, try swapping the oil out for lower viscosity oil ? even more mess. All back together again and sure, you guessed it "pop" ? all over me, the bike and the drive again. I am now ready to hang up my boots *sad2*.
Well after a cup of tea and tranquilisers and a good clean, I decided to check through for blockages, oil filter off, filter pressure relief in the filter working ok, blew through all the pipes with air ? no blockages there seems to be nothing wrong? Well last thing to check for a blockage is the filter head can't be anything here I thought this is new! You would not believe it but they had not drilled the return oil way completely through, no wonder the oil filter popped its gasket! Everything off again, drill out the filter head clean and put back togeter AGAIN and yuup, all working fine. Typical, even though I had immersed the filter head in cleaner and throughly blown it off before fitting, I simply forgot to check that the holes went all the way through!
I shall contact Draganfly on monday so they can perhaps look at the other filter heads they have in stock before there is another victim. A bit ***** about the worm, and lock nut as I wanted to replace these with the pump, poor quality control or perhaps non? Perhaps the ones from SRM are better?
All's well that ends well *smile* *ex*
Nigel
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If the timing side bush is "very worn" you are making a mistake by not fixing that problem and not very carefully checking the big ends with the crankshaft out of the bike.
SAE50 oil is usually too thick when cold, for satisfactory use in ther UK, but this problem of sealing rings blowing out of filters is a new one on me.
I've been wrong before, but I think you are on course for a mechanical disaster.
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Appreciate the comments, but the main will have to wait. We have glorious weather here 25-30C so I am off out for a run! If you see a load of bits on ebay for sale then you will know the worst has happened. All going, well I will strip it over winter - does anyone know where I can get an engine from ? rebuilt or not?
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Well finally got the GF fired up this evening...after a cup of tea and tranquilisers...
If you see a load of bits on ebay
LOL
Nigel, great reading. All those totally unexpected things that happens, will happen, and can happen, always adds something special to the adventure of riding, owning & maintaining!
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Hi John,
Thanks for the comments. I think I have had my fill of the "unexpected" for now, just need some good weather and NO problems *smile* When it all happened yesterday, I almost burst out laughing myself. When the filter ring popped out for the last time, I was bending down, looking closely to see what was happening, at least the oil was clean! If I had been watching from a distances, I would have burst my sides laughing.
As you say all part of the fun *ex*
PS what is the type of the "smaller" oil filter you mentioned earlier as I will fit one when I next change the oil?
Nigel
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Hi Nigel,
The filter I am using with the adaptor is from a peugot I think? Coopers Z2177, I think most filters are pretty interchangable now??
If you have difficulty finding the adaptor let me know I can get them from an electrical factors near here
There was another post recently about the crank nut/ worm not fitting
A good cycle shop will have a 9/16 X20 LH tap for reclaiming pedal crank threads (same as worm/nut)
Hope you get some enjoyable miles?
I did a couple of hundred yesterday on my SR, Very enjoyable vintage run in west Cork, there were 4 other A10's there
Mines the nicest tho!!! *smile* *smile* *smile*
At last we are having some fine weather
Regards
John
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John,
Thanks for the information on the filter. I went out for a couple of hours yesterday and had a good run, took it nice and easy and she is basically running lovely - the sound is simply fantastic.
I spoke to them at Draganfly and suggested they inspect their "nuts" *smile* and will send the worm and half nut back. SRM are sending me new ones, thought I would also add a new pressure release valve to the order.
Thanks for the tip on the cycle shop - was wondering how to get my hands on a tap.
Thanks also to all who have helped me get the GF back on the road and I really appreciate the forum super! Next job is the slipping clutch but I will start a separate thread for this.
Thanks
Nigel