A10 SR Serious Smoking

[BeezaDan]

Good points Swarfy,
Will check absolutely everything. Now have your points on a list that's getting longer every day.
Cheers,
Dan,

[BeezaDan]

Hello All,
Hope you're all ok in these troubling times.
 
Well, Engine now stripped and forensic investigation (to date) completed.

Confirmed - A previous owner had had a full bottom end and barrels Rebuild done by SRM, new high capacity pump, SRM piston type PRV, end feed crank, s'trap cleaned and hex plugs fitted, dynamic crank balancing, SRM roller+ball timing side bearing conversion, billet rods, barrels blasted and stove enamelled, bores taken out to +.060, new SRM cam and followers etc, - lovely job.

Recap on earlier issue and actions - Engine smoking very badly so top end stripdown - Bores found badly scored so honed true and new pistons + rings fitted. Head cleaned and checked, valves re-seated, new SRM tappets.
Top end rebuilt. (Honing took bores to just beyond limit for +.060s and rings, my decision to try it).
Static test run confirmed still smoking, possible problem with oil scavenge/return side.

Latest Findings - Big end shells badly worn and scored with excessive clearence. Some debris in the sludge trap.
Detailed checks on:- Cam, cam bushes, followers, rods, bottom end bearings, crank bearing journals oil pump, PRV, - Show all are ok.
Crank big end journals showing some surface scoring.

Conclusion - Superb bottom end and barrels rebuild by SRM ruined, most likely by subsequent use of detergent 20w 50 or similar oil (guy I bought it from said that he was using modern 20/50 in it), and running it without first cleaning out the oil tank, that's the kicker.

Thank heavens previous owner didn't use it much and that I thoroughly cleaned out the oil tank when I got the bike, plus its fitted with a cartridge oil filter, which limited the damage.

Now to thoroughly clean out or replace the oil lines and all of the oil galleries. Replace valve guides, replace all oil seals, get the bores sorted properly, clean out the oil tank (again), re-check everthing and then rebuild.

Will take time to get all of this done, so next instalment will be a while away. Great how all of the old A10 experience has come back, helped a lot by your suggestions and ideas.
Thanks and stay safe guys,
Dan.

[Jules]

I'm confused Dan, I thought the smoking issue was worked out to be due to the bore/piston sizing and scoring of the bores, is that the case? if so, then the teardown was to check everything else was ok because you had to fix the bores and piston issue anyway...is that right?
It sounds like whoever did the work previously wasted the effort by not thoroughly cleaning out after the machining, rather than "just" not cleaning out the oil tank, particularly if there is a cartridge oil filter in the supply side too, that should trap anything from the tank...
I'm also unsure why you would blame the oil for this, a good quality 20-50 with detergent scavenging in conjunction with the cartridge filter, should by all accounts be a very effective oil supply, I would have thought....

[Black Sheep]

Would be most surprised if just some crud in the oil tank would do that. I would look elsewhere.

[BeezaDan]

Hi Both,
Not blaming modern oils at all, they are excellent for engines designed with them in mind and having modern oil filters. They do the job slightly differently to 'mono' non-detergent oils (also excellent) where contaminant debris is concerned. Modern oils with detergent additives tend to break up and 'release' lumps of crud which would then be dispersed into the oil flow allowing a cartridge or other oil filter to catch it all.
In this case the crud in the oil tank may have been happily sitting there minding its own business until the addition of modern detergent additive oil did the job its designed to do and released it. That release would have been directly from the oil in the tank into the oil feed to the pump and then the main bearings and the inside of the crank case. (My cartridge oil filter sits on the return oil path to the tank, so would not have caught this debris before it got to the pump and mains).
Where max effect/damage would be inevitable. This would explain why the mains have been so badly affected. That accelerated wear then increased the clearence between the big end shells and the crank journals which then allowed the fantastic SRM high capacity pump to deliver masses of extra oil into the bottom end. That extra oil with its load of bits of crud scoring the bores and overwhelming the piston rings and causing the excessive smoking issue.
This is what I believe has occurred this time and if I am right it really reinforces the importance of cleaning out the oil tank thoroughly.
Anyone agree?
Cheers,
Dan.

[berger]

just my two penneth,  I had some cases soda blasted a while ago and decided to use a syringe to blast petrol through the oil ways, then blast compressed air through them. this was done until the petrol was coming out clean. after that I remembered someone mention the crud that hides behind the plugs that are used to cap off the drillings so carefully drilled them out. the one above the prv was hiding loads of crap that run out on the drill bit and could be drawn out into the oil when the bike was in use. so I got some small diameter long cleaning brushes and found loads more crud removed from these oil ways. I didn't drill out the one below the timing gears with the little spray hole next to it because it is a bit difficult but the others were all drilled out , oil ways cleaned and new plugs made . I tapped the holes and made small threaded ally plugs which will be screwed in with Loctite . I am glad I found all the hidden crud!

[RDfella]

Dan - agree with your detergent / non detergent analysis. Something I've been banging on about for years. And it's not simply an opinion, I've seen old engines destroyed in a matter of hours by filling with modern oil. As you say, a high detergent oil keeps dirt (most of it abrasive) in suspension, where it then gets trapped by the oil filter before reaching the engine - in a modern engine. In our old engines, a high deteregent gives a double whammy - it also dislodges the crud lying around the oil tank and engine and, as you say, this abrasive mix is then circulated around the engine until something wears out. Old non-detergent oils were designed to let the crud sediment out, where it could be extracted at intervals (my old Riley car handbook recommends dropping the sump every 10,000m to clean out sludge).
The answer is to always use an oil the engine was designed for. The older ones (like ours) often have minimal or no filtration - certainly not pre-flow and are not suitable for modern oils. Nor are they suitable for the viscosity modern engines use - nowadays as low as 5.
Horses for courses as they say.

[Triton Thrasher]

Superb bottom end and barrels rebuild by SRM

How do you know?

Don’t let your assumption about “death by detergent” blind you to other possibilities.

[BeezaDan]

Hi TT,
Well, when you have taken everything apart, inspected it all thoroughly, looked at the history and the evidence, taken advice from others who know the subject and applied it, what's left is likely to be the answer.
Very interested in what you think the cause of the smoking is, What's your diagnosis?
Cheers,
Dan.

[BeezaDan]

Hi berger,
Yes, I have gone through the plugs as you did. I didn't find much crud behind them though. Probably because there wouldn't have been enough time for it to build up too much and I used a very good solvent pressure fed through the oil ways. I certainly found the worn off white metal from the big end shells, very sparkly solvent!
Thanks again for your input, I might not have thought of that one.
I will be continuing to inspect and clean until I am 100% sure that every part is crud free before I start the rebuild.
Cheers,
Dan.

[KiwiGF]

A couple of observations on this which readers may or may not agree with!

1. Having a main bearing and/or big ends with excessive clearance does not necessarily increase the flow of oil into the crankcase, the pump (in theory) will pretty much pump the same volume regardless of the resistance to flow, the scavenge side will ALWAYS be able to pump more than the supply side, so as long as a high percentage of the scavenge side oil gets returned to the tank then there will be build up of oil in the cases (so this means only a little return oil must go to the rockers, and the scavenge side pick up pipe must not have leaks).
2. Particles bigger than the bearing clearance won’t pass through bearings and cause scoring of the surfaces, so in the case of big ends particles bigger than (say) 0015” will stay in the sludge trap. This begs the question of how does scoring from dirty oil occur, and my guess on that is, after the clearance has increased for another reason, and then is big enough enough to let larger particles through. Scoring can also be caused by the break up of the bearing surface if course.

As to whats happened to this engine? Pretty clearly it smoked due to barrel wear, how many miles has it been since it was rebored? The big end wear sounds more likely to be oil starvation than dirty oil, so I would check the end feed is as it should be (and of course there is always the possibility the PO had a valve in the supply side to stop wet sumping and forgot to turn it on once ).

Just my 2 cents worth!

[BeezaDan]

Hi KiwiGF,
Thanks for your ideas, appreciated.
The test I did by doing a quick engine run with the sump plate off (see earlier post) confirmed that a serious amount of oil was ending up in the crank case. Certainly more than was being pumped back to the tank. As you say the end feed has to be a suspect as well as the scavenge/return side. So I will be replacing the end feed seal and checking the return path carefully pre rebuild.
Its very evident that the SRM high capacity pump is capable of flowing as much oil as the clearences around the engine will allow.
Agree that debris bigger than clearences won't get through but as the clearences wear bigger more crud will find its way past, slowly increasing the clearances, - a vicious circle. Given my findings of debris during the parts cleaning process, it was definitely getting past the big end shells. (Yes, they are completely shot and were adding to the crud).
I did find some crud in the sludge trap but not much, probably the detergents in the oil carrying most of it onwards and back to the oil fiter on the return side.
Also agree that barrel wear is one of the main causes for the smoking, exacerbated by the abnormal amount of oil in the crank cases from end feed seal and/or the big ends.
As I said in an earlier post, this looks like a 'perfect storm' of several contributing factors.
One thing is for sure, as a direct result of this experience, I am going to know a heck of a lot more about the A10 engine, what does and doesn't suit it and how it really works than I thought I did.
Cheers,
Dan.

[trevinoz]

I have said this before but here we go.
The last A65 and Triumph engines in the 70s were specified for 20/50 multigrade oils.
These engines are virtually the same as our older engines.
If everything is cleaned properly I see no issues with using these oils.
I have been using them for many years now with no problems.

[berger]

I love sawing into paper filters and having a look what's in there, very satisfying - nearly as good as plain chocolate biscuits quickly dipped in a cup of tea

[chaterlea25]

Hi Dan,
Do not forget to dismantle the pressure relief valve, Any debris can jam them open and it's all downhill from there

John