Author Topic: A10 SR Serious Smoking  (Read 1422 times)

Offline BeezaDan

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A10 SR Serious Smoking
« on: 21.10. 2020 22:47 »
My SR (+060 bores, 9:1 pistons, SRM oil pump, SRM billet rods, etc) started to smoke (blue white) really badly.
Before stripping anything down, Checked all the things suggested on this and other forums.
Nothing serious found but did find that the tops of the pistons both sides went from looking normal matt black to wet black and both plugs furry black.
SRM sump plate with removable sump plug installed a while ago so removed plug and about a third of a pint of oil drained out. Fitted magneto cutoff type anti-wet sumping valve.
I have a toolbox mounted cartridge oil filter, also suspect that some oil is seeping back to the sump from that.
I suspected very rich running so moved jet needle down a notch and reduced main jet size.
Didn't help, it just produced weak mix so restored main jet, left needle in new position. Now plugs looking black shiny wet. (Small step forward?).
Still smoking like a steam engine. Decided to take head off, which confirmed piston tops wet with oil.
Checked bores, both showed vertical scoring front and back and also very shiny (like chrome).
Barrels off, both pistons also found to be scored plus signs of over heating around tops, rings looked ok but showing wear. Head gasket showing signs of some cross-cylinder leakage plus slight possible leakage cylinder to push rod tunnel.
Honed out bore scoring and restored both bores to correct honed surface (medium grit stones and oil wash during process), replaced pistons and rings with Gandinis at 8.5:1.
Always thought that 9:1s were perhaps a bit ott for a non-race bike, so 8.5:1s from Fecked seemed a reasonably sensible alternative.
Refurbished head, new valve springs, valves all ok and properly lapped in. Top oil feed banjo bolts looked to have slightly oversized oil holes so replaced with standard bolts.
Engine top end rebuilt (all new gaskets). Oil tank flushed out and filled to line with 'running in oil'.
Dry compression test showing 130psi both sides, repeat as a wet test (WD40 both bores) showing 165psi both sides. (Throttle and air valve both full open).
Noted that oil pressure gauge showing increasing and good pressure during pressure testing.
Good spark both plugs, timing checked and spot on.
Several days of careful work done and wallet empty, tomorrow's 'put some fuel in it and get it started' day.
I'll update you on results, wish me luck.

Hi Greybeard, thanks for the welcome and hello all, Part 2 -
Well, fuel in, started third kick, sounds great and running well, small oil leak from front rocker feed bolt, quick tighten and fixed. Oil pressure rapidly up to 55psi where the oil PRV cut in and dropped it to 50psi.
So far so good but (there it is Greybeard) Unfortunately that's about as good as it got.
Still smoking like a traction engine, - drat!
Had a think and decided to clamp the rocker feed pipe to see if there was any improvement to the smoke situation, Answer no.
Then decided to take the sump plate off add an extension to the sump oil pickup pipe stick the end of that into a jar of oil in a big drip tray and run it again. That showed a lot of combustion blowby (lots of combustion gasses coming out) also huge amounts of oil cascading out.
Conclusions - Clamping the rocker feed pipe probably means that the valve guides are ok.
Blowby and crankcase gasses probably indicating that the bores are now just that bit too big for the new pistons and rings. (Thought I would get away with slightly larger piston to bore clearence and ring gaps, not sure now that it was worth a try).
Volume of oil draining out could mean big end shells need replacement, (SRM oil pump able to push a high volume of oil out through the big ends?)
If crankcase pressure was forcing oil up the bores past the rings not sure why it was still smoking badly when running with the sump plate off, Unless it was residual oil in the combustion chambers.
Looks like another strip down (full this time), replace liners etc, check big ends, and double check everything else.
All very disappointing but lessons learnt and no doubt more to be learnt.
I had an A7 and then A10 GFs back in the 70s, lots of stripdowns in efforts to gain more power (as we did then) and of course as a result of pushing too hard. Never had a single moments problem with the oil systems. Hence this experience being an unwelcome surprise.
Now to start saving up.






Online Greybeard

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Re: A10 SR Serious Smoking
« Reply #1 on: 21.10. 2020 22:57 »
Hi, welcome.
I read all that expecting a BUT at the end. I'll keep fingers crossed for tomorrow.  *good3*
Greybeard (Neil)
1955 Golden Flash, sprung frame
Supporter of THE DISTINGUISHED GENTLEMAN'S RIDE https://www.gentlemansride.com

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A Distinguished Gentleman Riding his 1955 Plunger Golden Flash

Online RichardL

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Re: A10 SR Serious Smoking
« Reply #2 on: 22.10. 2020 16:15 »
Dan,

My kneejerk reaction would be: "Who are you and where are you from." Nevertheless, welcome to the forum. *welcome* Try to get over to the intros page and, uuh, introduce yourself. Helps keep things friendly.

As for the smokong problem, while I'm not one of to sharpest mechanics on this here forum, I'm going to pose a couple of questions regarding the head rebuild. Whenever a bike is described as being so thoroughly rebuilt as yours, we end up left with little else than having to question that work when a big problem arises. Would we recognize the name of the shop? Is it a certainty that the intake valve guides are a perfect fit in their holes and around the valve stems?

I'm darn near certain others are about to chime in with other potential problems.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.


Offline BeezaDan

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Re: A10 SR Serious Smoking
« Reply #3 on: 22.10. 2020 17:08 »
Hi Richard,
Thanks for your comments. I'll do a bit on the intros section at some point, always friendly with those who are friendly back!  I am still learning how to use this forum, my objective to share experience, learn from others of like mind and perhaps also to help someone else in the process.
Also agree with you ref always worth questioning the work.
You push the limits, - sometimes you win, sometimes you lose, that's life and learning.

Offline metalflake11

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Re: A10 SR Serious Smoking
« Reply #4 on: 22.10. 2020 20:04 »
Hello Dan.

There will be plenty of help along soon enough!

I wouldn't have though there was much wrong with the bores if you're getting 160psi?...... Maybe an engine breather problem, but that's not my best area of knowledge others will know far more than I.

Anyway, off for a think while I eat my tea.
England N.W
1960 A10
England

Online RDfella

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Re: A10 SR Serious Smoking
« Reply #5 on: 22.10. 2020 20:35 »
Have you tried one of those nicotine patches? They're supposed to stop smoking.......
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Online edboy

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Re: A10 SR Serious Smoking
« Reply #6 on: 22.10. 2020 21:29 »
keep out of low emission zones on your travels.

Online berger

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Re: A10 SR Serious Smoking
« Reply #7 on: 22.10. 2020 22:09 »
hello and  *welcome* beezadan have your bores become considerably oval, or you left a bit of lip in and broke new rings *dunno* Gandini rings usually sort everything except covid19 out *sarcastic*

Offline BeezaDan

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Re: A10 SR Serious Smoking
« Reply #8 on: 22.10. 2020 23:02 »
Hi berger,
From what I have read about the Gandinis you're right. I really thought that they would work their magic and the problem would be gone. Bores could be oval but were checked after honing and were round and consistent size tops to bottoms. Definitely no lip at top or bottom.
I had a thought, if SRM end crank direct oil feed has failed, might explain the amount of oil coming out of the bottom plate when I did the open crankcase running test earlier.
Can't explain why the smoking didn't reduce during that test as there would have been no pressure to force oil up the bores.
Similar question If its oil working down the valve guides, clamping the rocker oil feed pipe should have reduced the smoke.
This is a real puzzle.  Going to talk to SRM to see if they have any ideas.
Thanks for the pointers, at this point any constructive ideas are welcome.




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Re: A10 SR Serious Smoking
« Reply #9 on: 22.10. 2020 23:21 »
what piston to bore clearance have you ended up with and did you run it long enough with the rocker feed clamped off, mind you it could be anything because mine ran with no oil pressure and no feed to rockers for an age and had loads of piston slap and scoring and deep scoring by a circlip and when I put the oil pipes on the correct way it didn't smoke but it had to be stripped and fully re-furbished  [ flat cam and followers plus other horrors ] , except the valve gear which was all good

Offline BeezaDan

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Re: A10 SR Serious Smoking
« Reply #10 on: 22.10. 2020 23:40 »
After honing ended up with .018 thou piston to bore and ring end gap of .020 thou. Given that I got 165psi on the WD40 wet pressure test I figured that the pistons and rings were probably working fine.
If I had seen low pressure I would have called it a day at that point.
Thinking about possible end crank feed failure, if it has failed the SRM high capacity oil pump must be able to provide 55psi even with the failed end crank feed seal. I don't know if that is possible.
So many questions.............
I think that this is going to end up needing a full stripdown and investigation to find out what's going on, unless anyone else has gone through this and has a diagnosis/solution.


Online ironhead

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Re: A10 SR Serious Smoking
« Reply #11 on: 23.10. 2020 00:00 »
After honing ended up with .018 thou piston to bore and ring end gap of .020 thou.


 *eek* *eek* *eek* with that piston to bore clearance, its nearly out to the next over size *conf2* . might pay to re-check your mesurments.  should be around 0.0045 / 0.006"
SA

Online RichardL

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Re: A10 SR Serious Smoking
« Reply #12 on: 23.10. 2020 00:12 »
Mine are out to almost 0.008" following new rings and still running strong after about 4,000 miles. Not recommending it, but at 0.060 pistons it was worth a shot. Goes through oil, but does not smoke significantly. 

I'm shy about acting as if I know for sure the answer to any tricky or mysterious mechanical problem just by description. Nevertheless, I'm pretty sure the explanation here has to include a logic that gets oil into the combustion chamber while the compression is 165 PSI (or even 130). Is there such an explanation that could be attached to a quill feed failure and an empty sump. If there is, I don't know it (among billions of other things I don't know).

Hey, this just occurred to me, and may be completely useless. Are you running some kind of offbeat or specialized oil?

Richard L. 
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.


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Re: A10 SR Serious Smoking
« Reply #13 on: 23.10. 2020 00:15 »
wow 18thou *eek* were they slapping you in the face, mine were clanging away and hammering themselves  at 8thou

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Re: A10 SR Serious Smoking
« Reply #14 on: 23.10. 2020 00:20 »
wow 18thou *eek* were they slapping you in the face, mine were clanging away and hammering themselves  at 8thou


Bergs,

Not answering for Dan, but since you mention 8 thou and a lot of slapping, makes me wonder if mine are less or yours are more. I don't think mine are hammering.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.