Author Topic: Advice needed - engine tightening up - help - tips  (Read 14528 times)

Offline nigeldtr

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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
1951 Golden Flash (engine now rebuilt) 1953 M21 a pain to start and 1961 GF that is turning into a black hole!

Offline A10Boy

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Re: Advice needed - engine tightening up - help - tips
« Reply #1 on: 13.06. 2009 18:37 »
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.
Regards

Andy

1960 A10 - Black Golden Flash
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Offline nigeldtr

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Re: Advice needed - engine tightening up - help - tips
« Reply #2 on: 13.06. 2009 20:29 »
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
1951 Golden Flash (engine now rebuilt) 1953 M21 a pain to start and 1961 GF that is turning into a black hole!

Offline A10Boy

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Re: Advice needed - engine tightening up - help - tips
« Reply #3 on: 13.06. 2009 23:45 »
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.
Regards

Andy

1960 A10 - Black Golden Flash
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Offline dpaddock

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Re: Advice needed - engine tightening up - help - tips
« Reply #4 on: 14.06. 2009 00:08 »
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

David
'57 Spitfire


Offline trevinoz

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Re: Advice needed - engine tightening up - help - tips
« Reply #5 on: 14.06. 2009 00:08 »
Nigel, if the engine has only just been rebuilt, it sounds like there may not be enough piston clearance.
Trev.

Offline nigeldtr

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Re: Advice needed - engine tightening up - help - tips
« Reply #6 on: 14.06. 2009 08:32 »
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
1951 Golden Flash (engine now rebuilt) 1953 M21 a pain to start and 1961 GF that is turning into a black hole!

Offline MikeN

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Re: Advice needed - engine tightening up - help - tips
« Reply #7 on: 14.06. 2009 10:23 »
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

Offline nigeldtr

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Re: Advice needed - engine tightening up - help - tips
« Reply #8 on: 14.06. 2009 14:20 »
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
1951 Golden Flash (engine now rebuilt) 1953 M21 a pain to start and 1961 GF that is turning into a black hole!

Offline nigeldtr

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Re: Advice needed - engine tightening up - help - tips
« Reply #9 on: 14.06. 2009 16:02 »
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
1951 Golden Flash (engine now rebuilt) 1953 M21 a pain to start and 1961 GF that is turning into a black hole!

Offline raymo

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Re: Advice needed - engine tightening up - help - tips
« Reply #10 on: 14.06. 2009 16:32 »
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
DA10 Sr ( 1961  I think :-) )
B25S Starfire 1969
T500 ( the suzuki 2T Beast ) 1972
XLV 750Rf Honda current ride
ok so only the Honda is working :-)

Offline nigeldtr

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Re: Advice needed - engine tightening up - help - tips
« Reply #11 on: 14.06. 2009 16:59 »
Ray,

Is there any way to check this without stripping the engine?
1951 Golden Flash (engine now rebuilt) 1953 M21 a pain to start and 1961 GF that is turning into a black hole!

Online RichardL

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Re: Advice needed - engine tightening up - help - tips
« Reply #12 on: 14.06. 2009 17:01 »
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.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline nigeldtr

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Re: Advice needed - engine tightening up - help - tips
« Reply #13 on: 14.06. 2009 17:45 »
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!
1951 Golden Flash (engine now rebuilt) 1953 M21 a pain to start and 1961 GF that is turning into a black hole!

Offline LJ.

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Re: Advice needed - engine tightening up - help - tips
« Reply #14 on: 14.06. 2009 18:46 »
Nigel... Love the comment...
Quote
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!
Ride Safely Lads! LJ.
**********************
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red