Author Topic: A10 SR Serious Smoking  (Read 1072 times)

Online berger

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Re: A10 SR Serious Smoking
« Reply #15 on: 23.10. 2020 00:29 »
hi Richard mine were 8 when they were tinging away nicely but annoyingly , I finished them off on the cadwell run when I put the pipes on the wrong way. it didn't burn any oil when I put them on correctly , strange things happen

Online groily

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Re: A10 SR Serious Smoking
« Reply #16 on: 23.10. 2020 07:43 »
Agree 18 thou skirt clearance is way over the top, and if that's with the new pistons and measured at 90° to the gudgeon (wrist) pin, not good news really.  But if the smoke is and 'white and blue' still, and there's lots of it, it does suggest to me that there could be something on the inlet side. Not excluding any of the other possible causes, of course.

I don't know if it's even possible (just thinking on the keyboard really  . . .) but could the head have a tiny crack from the inlet tract to the pushrod tunnel, just conceivably?
I pose the question because exactly that caused me months of head scratching on another bike, where there was loadsa smoke everywhere and no obvious cause. Having done all the things you have (with better bores mind you!), and not achieved any real improvement, it turned out oil was being drawn into the inlet tract (which had been ported and polished a bit by a PO), via a pinhole/ crack.
Bill

Online Greybeard

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Re: A10 SR Serious Smoking
« Reply #17 on: 23.10. 2020 09:34 »
Just a thunk from me. Might the petrol be the culprit?

Offline Swarfcut

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Re: A10 SR Serious Smoking
« Reply #18 on: 23.10. 2020 09:37 »
The more I read through this its like the Bermuda Triangle. The mystery is simply explained when all the relevant facts are presented.

 We have scored pistons. Was it run without an air filter, scoring from road grit or dirty assembly is par for the course in this case.

 Evidence of poor head gasket sealing, as Mr G relates, possible path for oil into unwanted places.

 Bores smoothed and worn rings. A consequence of running too rich, the phenomenon of bore wash, more correctly fuel wash, almost neat fuel removing any lubricant from the bore. (Yes GB.)

  Oil filter, is it plumbed in before or after the T to the rockers? After the T will send oil back to the motor in preference to the tank and overwhelm the scavenge system.

 The result of the pipe in a pot test showed lots of oil coming into the crankcase, how did this compare with the ability to scavenge? An air leak on the pump or blocked/obstructed pipe and pick up valve are possibles. The capacity of the scavenge side should deal with like for like volume on the supply side.

 With a piston/bore of almost the next oversize its remarkable it runs at all, the compression rings are working fine a kickstart speeds, but the remedy will be another block rebored correctly to suit your best pistons, certainly cheaper than a resleeve and more new pistons to suit.

 I think its a complete tear down and an almost forensic examination of every component. I'm sure the answer will be simple but possibly elusive.

 On a lighter note, this may be of  use.

https://www.hastingspistonrings.com/tech_tip/fuel-wash-how-to-eliminate-this-potentially-serious-problem/#:~:text=There%20is%20a%20condition%20that,%2C%20pistons


Swarfy.


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Re: A10 SR Serious Smoking
« Reply #19 on: 23.10. 2020 12:55 »
greybeard I was thinking has someone sneaked up and poured oil in the petrol tank , it's nearly trick or treat time *evil*

Online RichardL

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Re: A10 SR Serious Smoking
« Reply #20 on: 23.10. 2020 14:06 »

 With a piston/bore of almost the next oversize its remarkable it runs at all, the compression rings are working fine at kickstart speeds...

That's a really interesting point and some next-level thinking (to me, at least).

Richard L.
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Offline BeezaDan

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Re: A10 SR Serious Smoking
« Reply #21 on: 23.10. 2020 14:14 »
Hi All, thanks for your welcomes and useful comments.
 Swarfy, thanks for the analysis. You are probably right, (Looks like I didn't get away with it).
It does run really well with not much piston tinging, probably because there's so much oil around in the lower bores. I'll investigate along the lines you highlighted ref oil filter and scavenging etc. Oil filter is in the line before the T. Pick up/scavenge pipe ball valve appears ok, ball is where it should be and free.
Previous owner did run it without an air filter so its possible that the bore & piston scoring I discovered was caused by that. He also had it running far too rich, biggest main jet I have ever seen in an A10! As you said, very effectively washing the bores!
Hoping not to have to reline but at already +.060 if I remember rightly going to +.080 is a probably not a good idea on an A10?
Groily, your idea ref a hidden head crack (expanding as it heats) could be an explaination for the increasing blue white fog. I'll look for cracks during the investigation.
Also changed fuel in case there could be contamination, that would have been a really easy solution, (why is it that life is never that easy!)
My gut feel right now is that this is going to end up being a perfect storm of contributing causes.
Yes, a full stripdown and investigation will be my next course of action.
Our friends in Wales are going into a full lockdown today so my conversation with SRM will probably have to wait. My engine problems are but a drop in the pond compared to what they are having to put up with.

Its great having access to some fresh perspectives, its like the old saying 'when you are up to your a...se in crocs, its easy to forget that your primary objective was to drain the swamp'.
Any more ideas that you can come up with are welcome, I will keep you all updated on any further progress as it happens and as I investigate your ideas on a cause.

Thanks guys,
Dan.





Offline Colsbeeza

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Re: A10 SR Serious Smoking
« Reply #22 on: 24.10. 2020 00:35 »
Hi Dan and Welcome,
I would like to add one more potential issue which happened to me. My rebuilt engine smoked heavily on the LHS pot. After two strip downs, I discovered that the LHS piston was tilted 0.010" to the right. The small end bush had been reamed at an angle. A straight edge across the barrel and a feeler gauge found the problem. Check that both pistons are level within 2-3 thou. Unlikely but worth checking.
Col in Oz
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Online Jules

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Re: A10 SR Serious Smoking
« Reply #23 on: 24.10. 2020 01:50 »
good lord Col, whatever made you look at something like that, thats a serious stuff up on a new piston....

Online Jules

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Re: A10 SR Serious Smoking
« Reply #24 on: 24.10. 2020 01:58 »
surely with those ring gaps and bore clearances, smoking would be inevitable, partic. as you have confirmed huge blowby too.....

Offline Colsbeeza

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Re: A10 SR Serious Smoking
« Reply #25 on: 24.10. 2020 08:32 »
Hi Jules,
I think one of the Forum members suggested it, and to check everything measureable. I cannot find the reference.
I passed both Gudgeon pins through until they touched, and there was about 0.006" misalignment.
After repair, I checked with a length of 19mm bright rod, which was a surprisingly good fit for an 0.75" Gudgeon.
Very pleased to find it!!
Col
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Re: A10 SR Serious Smoking
« Reply #26 on: 25.10. 2020 11:31 »
G'day Dan.
With 18 thou in the bore and 20 on the rings  *eek*
The WD test will seal for enough kicks to give good comp but not in a running motor. The hole in the left rod is squirting oil on the bore and splash from the right is getting past the piston & rings. Valve guides would also be suspect as it would take a fair while to exhaust all the oil up there after the feed is stopped.
Normally after stopping a motor there would be about 1 cup (250 -300ml) of oil in the sump.
Cheers
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Offline BeezaDan

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Re: A10 SR Serious Smoking
« Reply #27 on: 25.10. 2020 23:46 »
G'day musky,
I think you could be right. Part of the perfect storm I am dealing with is highly likely to be the over bores.
I am getting the liners replaced bored and honed plus pistons fitted by a specialist machine shop.
On further advice from members I am also checking the pump + crank end feed and also the scavenge side of the oil system as well as the small end relative alignment. Big end shells will be checked as well.
If that lot doesn't fix the problem.............I'll think some more...............and set fire to it........

Online chaterlea25

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Re: A10 SR Serious Smoking
« Reply #28 on: 26.10. 2020 13:44 »
Hi Dan,
Don't forget to clean the oil tank at least ten times *eek*
From your bikes symptoms it's likely that blasting grit was left inside it by the DPO

John
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Offline Swarfcut

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Re: A10 SR Serious Smoking
« Reply #29 on: 26.10. 2020 15:44 »
 CJ. On that basis Dan will have to take advantage of low rate finance and expect scored journals and a restricted  flow crank as well.

   One thing's for sure, there won't be many restful nights until the damn thing is down to the metaphorical molecules. Like I said, the Bermuda Triangle, but a good thought there that I had overlooked, we don't really know the full history and without that we can only speculate the causes of the problem.

  From earlier comments the timing bush may have excessive radial clearance now, and too much oil is being dumped into the crankcase. Worth checking the lift of the crank in that bush. Like CJ I'm thinking possible abrasive destruction on a grand scale. Hope I'm wrong.

 Swarfy.