The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Colsbeeza on 17.08. 2018 07:25

Title: Smoking
Post by: Colsbeeza on 17.08. 2018 07:25

My 1961 GF is on second oversize bore, and the LHS cylinder has been blowing smoke since startup after assembly. The guy who did the work assured me that he didn't crack the rings. The bike has only done 40 miles, so I was a little relaxed until now. However, that should be quite enough time to have reduced the smoke considerably. But No.! It blows clouds just after starting (every time), and does not completely go away.
Presumably CR should be about 7.5:1 wit the oversize and the Compression Tester should reach about 110 psig + a little for adiabatic heating.
I used my Compression tester today, and got 85psig on the Left, and 100psig on the right. After adding a few squirts of oil down the bores, the numbers changed to 120 Left and 115 Right. The Wet readings seem OK.
All this suggests that the LHS rings were cracked indeed, but the valves are probably OK.
My next job will be to pull off the head and barrels and take a Bo-Peep, being careful not to drop bits of ring down the crankcase. I will also deglaze the bores lightly if needed, as the RHS dry test may indicate that it is needed.
I have ordered a Leakdown Tester, but it seems that the Compression test has told me mostly what I needed to know.
One thing I do know - No one works on my bike except me from now on.! *angry*
Any further thoughts appreciated.!
Title: Re: Smoking
Post by: coater87 on 17.08. 2018 08:00
Hello CB,

 My motor has about 30 miles on it and still smokes out of the left side.

 I will run to 100 at least and see if it clears up slowly before I get too excited.

 I install the pistons in the cylinders, then  install the wrist pins in the pistons. My odds of breaking a ring are tiny.

 30 or 40 miles is not much on fresh rings and bores while trying to seat, and it sounds like we both break a motor in pretty gently.

Title: Re: Smoking
Post by: Triton Thrasher on 17.08. 2018 12:55
I tested mine recently and got a reading of 170psi on both cylinders.
Initially id id it with the throttle shut getting a reading of 130 but was told I should have the throttle open whilst testing compression.

170 psi sounds like a set of rings that have seated properly.
Title: Re: Smoking
Post by: Colsbeeza on 17.08. 2018 13:32
G'Day Lee,
I like the idea of putting pins in after pistons.
The smoke is way too heavy for me, so I will pull it down anyway.
I have done a few rebores & new pistons on various bikes & cars over the years but never had much smoke.
With Hondas, I would use pistons which were worn out of spec, but a hone and new rings never gave me problems.
Title: Re: Smoking
Post by: BSA_54A10 on 17.08. 2018 13:39
Individual readings are not much use unless you get a reading under 50 psi.
What is important is a set of readings over time so you can plot the wear in the rings & bore
Even better is a set of wet & dry readings.
When we ran the SR500's for work, they got a monthly measurement.
While the motor would happily run down to 95 psi then object all the way down to 70.
If the rings got done when it had dropped to 120 ( or less ) we could get 3 or 4 sets of rings out of the bore.
If left to much less it was rebore & new piston time

Also the actual number will vary according to the type of meter, type of connection , the rubber hose is always 10%  lower than the solid tube and the quality of the tool.
So a set with the same meter is the go.
A fun game is to get 10 different people to test the same engine, even using the same meter 1/2 of them will be different.
Unfortunately the calculator/computer age has causes way to much empathsis on the actual number and not the trend
Title: Re: Smoking
Post by: JulianS on 17.08. 2018 13:52
What make of rings were used?

The "new" hepolite branded ones have a bad reputation for quality. If you have those fitted that may be the cause of your problem.
Title: Re: Smoking
Post by: Colsbeeza on 18.08. 2018 00:57
Thanks Trev, That seems a great strategy to lengthen the life of the bores, and it does emphasise the problem of running too long with low compression. I don't think I have the luxury of monitoring it over time just yet. The readings explain the severe smoking. I am not prepared to ride it for another 100 miles or so and then discover it has broken rings or something else. I don't want to risk further damage and I wouldn't enjoy the riding anyway. The thought of thick carbon jamming up and down on my new bores leaves me cold. ( a vivid imagination can be a curse at times ) Best I find out now, fix it and enjoy the running in.
In 1980 I purchased a new Chrysler Sigma wagon when the first baby was born. It burnt oil for 186,000 Km. Of course, the company said that 1 liter loss per 1000Km was within the normal range. *lol* I found out it had chromed rings and Nikasil bores, so it was never going to bed in - not with my driving style anyway. The pistons took me hours to clean up. I honed the bores and fitted cast iron rings for a total cost of A$114. It never burnt a drop of oil thereafter, even from the first day.
Julian the rings were Hepolite but purchased about 25 years ago. I still have / had the box until recently, but a scrounge in my shed just now has not turned it up. Presumably the Chinese were not making them ten.?
Can you suggest a source and brand of good quality rings.?
Title: Re: Smoking
Post by: BSA_54A10 on 18.08. 2018 07:51
I have been using dry fitted rings now for around 20 years and can thoroughly recommend doing it that way.
Musky fits his dry as well.
Running in consists of one lap of the block, about 3/4 mile.
What kills rebores is starting the engine then frigging around for 20 minutes with the engine idleing as you attempt to adjust the carb.
After a couple of minutes of no load running the bore has already started to glaze.

So it is on with the riding gear kick / push start, starting fluid, whatever it takes then a hard run around the block with lots of wide open throttle up & down through the gears.
After that back in the shed for a cool down & retorque then around the block a second time , then back to the shed to do the tuning.

It should have been self evident to e that it was a waste of time trying to adjust a carb on an engine which was yet to seat the rings fully, but I am a slow learner.
I wipe the bore with an oily rag then wipe off with a dry one, wind the pistons into the barrels, tighten the flange bolts then off down the road
Title: Re: Smoking
Post by: ellis on 18.08. 2018 11:54
I recently fitted a set of GANDINI rings to the 850 commando and was very pleased with the results. No smoke and did a few full throttle runs to bed them in but kept the tacho below four thousand with good results.   *smile*

Title: Re: Smoking
Post by: RichardL on 18.08. 2018 13:58

After that back in the shed for a cool down & retorque then around the block a second time , then back to the shed to do the tuning.

This is where you lose me. Seems a liitle item like removing and replacing the rocker box is omitted from this fun afternoon.

Richard L.
Title: Re: Smoking
Post by: berger on 18.08. 2018 14:35
yes ellis I love gandinis , I've had rings that were shaped like 50p pieces that chucked neat oil out the exhausts. I blued the bores and pushed the rings up them and saw horrors of hit and miss contact. they were thrown over the shoulder and gandinis fitted , started the bike and not one bit of smoke *smile*
Title: Re: Smoking
Post by: trevinoz on 19.08. 2018 00:49
And don't get it honed too fine.
Title: Re: Smoking
Post by: BSA_54A10 on 19.08. 2018 06:14

After that back in the shed for a cool down & retorque then around the block a second time , then back to the shed to do the tuning.

This is where you lose me. Seems a liitle item like removing and replacing the rocker box is omitted from this fun afternoon.

Richard L.
Yet to find a way to access the head bolts with the rocker box on, but am all ears if you know one.
And FWIW the new rocker box gaskets ( if they are going to be fitted ) go on after the final torque down and yes it is a full day job.
One reason why to a large part I have given up on motorcycles with 1 or 2 redundant cylinders. *smile*
Title: Re: Smoking
Post by: Colsbeeza on 19.08. 2018 12:37

I think that frigging round has been my problem. Not my fault though.
I took the cylinders off yesterday. A quick inspection hasn't thrown up a reason. The bores and rings look good (none broken) and the bore cross-hatching is quite visible all round. The little-end bearings had been machined with tight tolerance to the gudgeon pins, and the pistons still did not rock back and forth without a little help yesterday. I will get the pistons off and have a good inspection over next few days though, as the rear of both pistons have lost their "frosty" or matt finish for a width of about 0.5 - 1cm  below the rings and are shiny in that spot. That may be normal?, or could that be due to the firm gudgeon pins?. I had also best replace the rings. Do you know where I can get Gandini rings.? A quick search on the internet hasn't solved that for me that yet. Not sure I should trust modern Hepolites from what I read on the Forum. Any other ring recommendations for a bog-standard GF which will not be raced, but will be a gentleman's tourer for Club events.??
Anyway re the frigging around - When the bike was first run back in November 2016, it blew smoke from the left cylinder and I guess were possibly not glazed at that stage. It had probably been started a few times in the workshop (not by me). I had some months earlier had the magneto checked. I then spent a year doing the wiring from scratch amongst other competing pressures ( I am not an electrician ), and all the other fiddly bits to get it running. When I eventually started it in October 2017, the bike was spitting badly, and would not rev. The left exhaust pipe was glowing red within a few minutes. After a few weeks of persisting and checking carb, timing, tappets and anything else that moves and starting it many times, I had the magneto rechecked again as a last resort. Yep it was out by many degrees - not explainable. This time I went to Sydney to pick it up and got to watch the magneto perform on the tester, and it was then firing within a half degree between cylinders consistently with good spark. 
To cut a long story short, the bike was probably started 30 or 40 times before I could get it on the road for a blast.  I was certainly aware of glazing bores but could not do anything about it. That is where I am at the moment.
Is that enough to explain the 85psi dry compression test on the left, and 100 on the right, and 120 left wet and 115 right wet.?? (
I think I may go down the path of dry rings, given that the rest of the motor has 40 miles on it. By that I hope you mean to assemble the pistons & rings without oil, but the circulating oil system as normal.? Just give it a blast before the rings get wet.?
Whilst I have it down, I will go through the many other possibilities I have not already dismissed. It does not wet sump, the tank breather is not blocked, I am using a 20W-60 mineral oil without friction-modifying additives. It has an external oil filter correctly connected. I had set the timing at 32 Deg BTDC, and I will retard that a bit to about 30 Deg to suit modern fuel. After all it is a bog standard 1961 GF.
I will also check the breather passage from the timing side. I am not sure of the status of the cork breather seal thickness. I will also remove the oil pump and check the gaskets. And Trev (inoz), I will give the bores another hone to clear the glazing.
That all sound good.??
Title: Re: Smoking
Post by: Colsbeeza on 09.10. 2018 02:50
Well I got the Flash back together after getting the guides replaced, faced the head, checked for cracks, freed up the little-end bushes which were too tight, de-glazed the bores, replaced the rings, and took it for a 5-mile run - fairly hard but variable. Since it had already done 40 miles, I extended this run a little. Good power, no unusual noises, pleasant to ride. The Clutch is getting a little stubborn though.
It is still smoking on the LHS much as before, although only one run. So I have come up with my strategy list of things to eliminate. My main suspicion is the breather system - perhaps worn cork or blockage, although piston/ring match can be a headache.
All the costly ones are done, but given what I found inside, I was too smuggly confident to complete the obvious things.
It will be a few weeks before I can get this done, as well as re-tensioning the cylinder base nuts and head bolts but any  additional ideas would be appreciated. BTW the pistons are 25yo Hepolites with only 40 miles on them. The new rings are AE Hepolite from SRM.
Title: Re: Smoking
Post by: Swarfcut on 09.10. 2018 08:37
 Just a thought to add to the mix. Have you checked the width of the piston ring grooves with the thickness of the rings? In case I am stating the obvious, as the piston descends, the ring rises to the top of the groove. Piston rising, ring moves to bottom of the groove. Too much gap here means you will have a very effective oil pump transferring oil from the bore to the combustion chamber.  This is one aspect we take for granted with new precision reckon they are made correctly. But either component is on the wrong side of accepted tolerance you will get problems. As the radial seal of the ring to the bore is reasonably OK, you have pretty good if unbalance compression. There should be the barest minimum of clearance between the sides of the ring groove and the ring. On a worn engine the rings can be worn to a "T" on its side profile , burn oil but still have good compression.  After the frustration and hassle  I would be inclined to nail it back together and get some miles in before the weather turns.
Title: Re: Smoking
Post by: Colsbeeza on 10.11. 2018 08:10
Thanks Swarfcut,
I measured the grooves and rings on both pistons. They are both identical and within spec for new gear. So why does one cylinder always blow smoke on startup and the other never has.
I have been away for a few weeks, so didn't do much anything on the bike. But I got into it over the last two days. I checked the breather, fitted a new cork but there wasn't anything wrong with the old one. Checked the breather passage, re-tensioned the head bolts, stripped the oil pump and detailed a few minor issues with it, checked the sump suction tube and ball, etc etc. There is nothing more I can do. And yes the left cylinder smokes exactly as it has been doing for the past 12 months.
I think that leaves me with just putting some miles on it in the hope that the problem will go away. If it is still smoking after 100 miles or so, then the only thing left is pistons.!! I could not see anything wrong with them, but that is all that is left to do.
Title: Re: Smoking
Post by: Ted_Flash on 10.11. 2018 09:42

Have you considered the possibility of a warped head/cylinder joint.  I had a smoking problem and ruled the head/cylinder joint out as I thought cast iron can't bend.  However they certainly had, and a skim sorted the problem.
Title: Re: Smoking
Post by: duTch on 10.11. 2018 09:48

 Mine periodically does a bit of that, but stops fairly soon- the other week it did it at the lights, but stopped same...... *dunno*

 only thing I can think of is don't look back ..... *bright idea*
Title: Re: Smoking
Post by: bsa-bill on 10.11. 2018 10:28
Mine periodically does a bit of that, but stops fairly soon-

Mine did too, almost every time it started it would smoke until maybe quarter of a mile then it would clear, then one day  through the winter when I started it and ran it for a while I noticed the smoke did not clear, turned out to be a broken oil ring.
Question is was it broken all the time or just when the smoke would not clear, (edit) well on reflection it does not smoke at all now since the rings were replaced
Title: Re: Smoking
Post by: Swarfcut on 10.11. 2018 11:12
 Colsbeeza...Reckon you have done more than enough to fix the smoke. It is certainly frustrating when through a combination of unrelated circumstances this is what you get.

   On the other hand it may be the only working example of that pesky li'l 'old oil hole in the drive side rod, doing its job of oiling that left hand bore on cold start until the oil pressure drops as the motor warms and the oil thins out.

  This gives you the bragging rights to demonstrate  it at every suitable moment..  Meanwhile, nail it back together and enjoy riding while you can.  Good chance it will settle down OK with use, as long as it smokes you know you still have some oil in the tank.

   Cheers, Swarfy

Title: Re: Smoking
Post by: berger on 10.11. 2018 11:39
I did not go to the pub! first Friday missed in months, anyway I will go today *beer* *countdown* back to some nonsense, colsbeeza at this stage in your fettling I would be inclined to stop the oil reaching the rocker box even though you say it has new bits , I don't know weather yours has cast valve guides or bronze BUT my top end was starved for 80odd miles with bronze guides and no damage done, I personaly would risk a mile or two up the road  . you never know it could tell you a story and help pinpoint the problem, good luck *beer*
Title: Re: Smoking
Post by: RDfella on 10.11. 2018 17:55
Colin - after your earlier post I was going to bet you wouldn't find a broken ring, but I got in too late to make the prediction. Like yourself, I've done many engines over the years, but have to say the A10 never ceases to surprise me. Quirky as hell. BTW, my right cylinder smokes for a few minutes after start up, but clears soon after. About 100 miles since rebuild now and it's improving. My pistons are JP. Looked cheap and in a cheap box (price wasn't) but I guess, as others have said, we should consider ourselves lucky we can at least get parts for our bikes.
Title: Re: Smoking
Post by: Colsbeeza on 11.11. 2018 11:23
Hi Ted Flash,
During my recent head rebuild, I got the guys to reface the gasket surface and I fitted a solid copper head gasket. I have had no indications of a leak, so I think that is OK. Berger, that idea crossed my mind today. I will cut off the rocker oil supply. If that fixes it, I'll know in 2 minutes without riding it. I suspect it won't, as I have the original banjo orifices (orifi?) of 1.14mm (3/64"). The guides are cast iron, so some inherent lubrication should avoid any troubles.
Today, I rode it 42 miles to get it inspected for Club Rego. I rode it down the driveway, and I looked back after 50 metres and a huge pall of white smoke would mean that any cars following would have to creep through it slowly. Thereafter I saw no sign of smoke. The missus said that it was white with a bluish tinge. No sign of oil from breather outlet either. Upon returning, I wiped my finger in the mufflers. The RHS was quite dry, but the LHS was oily and black with carbon (very dense like carbon-black) but the oiliness was quite thin, like the oil had been diluted with fuel. Any chance that I have a pinhole between the float chamber (LHS) and the inlet duct.?? Any fuel leakage would favour the LHS cylinder. Grasping at straws now I know and the smoke would not be white!! The left exhaust is showing a blue tinge, whereas the RHS is a light straw, so maybe a bit advanced on the LHS.
It ran well above 1/4 throttle, but the pilot circuit needs some tuning - a bit of spitting when hot.
The old rings were not broken but have been replaced with Hepolite rings purchased from SRM, so definitely not a broken ring.
Dutch for the next few rides I'll take your advice and not look back. Swarfcut, I'll forgo the bragging rights if I can stop the smoke.
Title: Re: Smoking
Post by: mugwump on 11.11. 2018 14:04
The moistness in the lefthand silencer is probably condensation, are both cylinders getting equally as hot during the first few minutes of running from cold. Can I suggest that the lefthand cylinder is not firing cleanly, for some reason.
Title: Re: Smoking
Post by: chaterlea25 on 11.11. 2018 20:52
Hi Col,
Although I have not come across a problem like this on BSA's , I once worked on a Tri**ph that smoked like a bastard
no matter how many pistons/ sets of rings I fitted to it *problem*
Eventually I spoke to an "old hand" about it, his answer went like this.....
"All them fkn cylinders go porus once they get the first rebore"
I found a new cylinder for it and fitting that cured the problem

Something else to try before ripping it all apart again
Try draining the sump before the next start up  *????*
If there is no (less) smoke after starting, the problem maybe oil draining into the crankcase
If there is excess oil in the sump this may point you towards a solution  *????*

It takes quite a long time/trip to burn off all the oil  that has stuck to the inside of the exhaust and silencer

Title: Re: Smoking
Post by: muskrat on 12.11. 2018 07:24
G'day Col.
I agree with John. The sump will hold about a cup full (250ml) after a run. Drain it, there will be enough in the cam trough to lube at start up. The pump will/should supply oil to the crank straight away so no fear there.
See if that makes a difference.
Title: Re: Smoking
Post by: Bsareg on 12.11. 2018 11:01
Years ago my 1960 mini engine became a real smoker so dropped in an exchange engine only to find it smoked worse than the original. I had a go at the supplier who assured me there was nothing wrong with the engine but to try it for a week. Sure enough the more efficient engine eventually cleared out the oil soaked exhaust and the smoke cleared. Its still going well........
Title: Re: Smoking
Post by: Colsbeeza on 16.11. 2018 05:03
Hi Mugwump,
  I don't think it could be moisture condensation, and both cylinders seem to warm up equally. She seems to have heaps of power, and I have tried new plugs (recommended Champion L82C ). This has been going on since first startup in 2015. Why moisture would favour one cylinder so extremely is beyond me. Thanks for suggesting it so will have to think further about that. John CL, I have drained and measured the sump many times, usually get about 150 mls even after several weeks, so I am happy it is not wet-sumping (surprising since I didn't know to check the crankcase non-return ball when I had it apart). I still drain the sump each time to make bl-- sure it is not the source of smoke. I have never got 250 mls as Muskrat has experienced. I haven't started it since my run last Sunday, so will be hoping the pipes don't hold much oil, although the LHS tail pipe was still wet with a black carbony oiliness when I got home. I am homing in on a basic flaw in the Left side piston, but your experience with the Triumphs is interesting. I honed both bores recently, and there does not appear to be any obvious pores, but if they are there, then probably too small to be visible. Given the amount of smoke, I think I would be looking for a fairly visible problem.?? It might be a good idea to find a set of cylinders in case I have to pull it apart again.
The bike has done about 85 miles on the reconditioned engine, so maybe I should not panic just yet.
 Think I'll retire to the shed and give it a kick in the guts and see how it smokes. I'll get a few photos.
Cheers Col
Title: Re: Smoking
Post by: chaterlea25 on 16.11. 2018 16:50
Hi Col,
There was nothing visible in/on the Triumph bore
A dye penetrant test might show up porosity? or maybe just heat the cylinder up after degreasing it and see does oil appear on the bore surface  *????*

If you start it with the sump drained and it still smokes,
I would remove the offending side exhaust pipe, shine a light into the port and look for evidence of oil
Maybe there's a score in the head in the guide bore and oil is weeping down there  *????*
(I have found that too *sad2*)
Look for the same on the inlet side, but this might show up as an oily plug??

It might be worth starting the bike with the oily side exhaust removed  *????* to see if there's "fresh" oil/smoke
coming from the engine *????*

Title: Re: Smoking
Post by: edboy on 16.11. 2018 19:16
i would second that. remove the exhaust and try to find where the oil originates. guides or piston.
i believe the old hepolite piston rings are tapered and if fitted upside down pushes oil up the bore rather than down it. i would check/measure the bore ring gaps at the 3 possitions in the bore. top , middle and top. however the main suspect would be a loose or scored valve guide. possible cracked head if ally.
Title: Re: Smoking
Post by: Colsbeeza on 18.11. 2018 11:38
Thanks John CL, That gives me a couple of things to try.
To recap, I have recently re-honed the cylinders, reconditioned the head - new guides and valves done by a very reputable workshop and head crack-tested. However, that doesn't necessarily solve the situation if there is a score in the head guide bore so that is still a possibility. The guy used a sealant - not sure what but used to help bed in guides, so should have sealed any score one would think.
Edboy, I also replaced the rings with Hepolite from SRM. Unlike my unmarked originals, the top of the rings were marked with a "T", so I can eliminate that possibility. As the bore had only 40 miles from the new rebore, there was no difference in ring gap at any position in the bores.
First step now will be to remove the exhaust pipes and have a decent look for oil sources. I'll plod along and get back to you before too long.
Cheers Col