Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board A65 problem with rings sealing

I rebuilt my A65 Lightning with new Emgo pistons and Hastings (IIRC) rings about 10 years ago, but never put any mileage on it. So I brought it our of retirement last week and took it out for some spirited runs. After some adjustments to side covers (that's another story) I got it oil tight, even when idling on the stand. However, after about a 100 new miles (total now of 300 miles since rebuild), it's now got so much blow by on the right cylinder that it coats the rear tire.

I disassembled it today to find that the rings sealed well on the left cylinder, but not on the right. Following are some photos which seems to indicate that the crosshatching on the left cylinder left by honing are still apparent, though it does not seem to have a blow-by problem. But on the right cylinder, the honing marks are almost non-existent, and the blow-by actually leaves oil on top of the piston.

Could the shop that bored it (+.060) have failed to hone that cylinder sufficiently?

Could the ring gaps being lined up have caused this situation (they seemed quite close to being lined up)?

If I re-hone that side, can I use the same rings over again? Getting new rings even from British Cycle right now is a problem.


cylinders showing honing marks

Close-up of right cylinder

Cylinder head showing oil fouling on right cylinder

Thanks for any advice.

Did you run it in carefully?

one piece or 3 piece oil ring ?
Sometimes a multi-piece Oil ring can get installed wrong .

Many years ago when I had my tiger cub rebored, I asked the the old school engineer how long to run it in for. His reply was "Twice up and down the bore"
Last year I asked about running in my brand new GM speedway engine, the engine builder replied "warm it up then thrash it"
So over the space of approximately 43 years the advice has not changed

Pics of rings please , are the RHS rings evenly matt allround? What are the ring gaps? Theres seems to b a lot of vertical scratches in the RHS , and a nasty patch near the top , if it was honed the marks should be clearly visible on the lower cylinder section beyond the ring travel.

Even in the left cylinder I don't see much of a cross-hatch honing pattern.
It may be the photo, but it looks messy and not what I would expect.
The right cylinder doesn't show any signs of honing at the same time and I agree with Gavin about the vertical scratches.
Also, are all those thousands of marks in the pic really there? Rust pits perhaps?

I don't know what tool was used to "hone" the left side, but I guess he chose not to repeat on the right side, so left it alone.

I'd suggest having it checked by a proper engineer for bore size/quality against the pistons you have.

No.

You can normally get away with it if you are brutal when you bed it in.

Looks like the head gasket was blowing that side so comp would be down, may explain some of it.

A few more photos. Tough to get good photos with the I Phone.



Here is the composite gasket I used upside down on the head. Yes there is a small dent in the head adjacent to the bore and a corresponding mark appears on the gasket.
I don't think the gasket was blown. The mottling pattern on the head is unusual to me so I'm blaming it on the composite gasket. It looks kind of like shellac or something that transferred from the gasket. I'll be using a solid copper one on the re-build.



Photo of the pistons with the rings. Not much scuffing at all that I can see.



I removed the top ring to measure the ring gap here. It's .013".


Andy, most of my builds go directly from my shop to the dyno, the road race track, or the Salt Flats, so wide open throttle. My road bikes go out on the road and get thrashed as well as I can on these back roads, up and back down the rpm scale. Is that what you would call run in carefully?

Nick, I could do that!

From Koan: "I'd suggest having it checked by a proper engineer for bore size/quality against the pistons you have."

I believe he best pros in the world on BSA's are right here on this forum. That's why I'm asking you guys for advice.

Tom

Measure the ring gap in the unworn part of the barrel near the bottom, if its 13 at the top expect it to be tighter at the bottom. If its not massively different then a fresh hone and new rings would do the trick.
Rings are supposed to rotate in operation, if they were all lined up that could just be a chance thing so long as they are free to turn, on a side note check the ring fit in the land, they should be free but not walloping around, if a 2 thou feeler goes in then the lands have taken a beating ( I dont think its that but its an easy check).

Does the bike breath through filters?, the vertical scores would suggest not, or the oil was dirty.

I believe I’ve caused similar issues as you by thrashing a set of standard rings. Following others advice to do this, but I guess one persons idea of giving the bike some hard pulls can vary to another. Does your oil tank stink of gasoline also?

Even with modern rings I prefer to use a running in oil and ride the bike normally.

The quickest way to get vertical scratches like that is to leave honing grit on the bore.

After honing, it has to be washed in soap and hot water until the bore surface leaves no mark on a white paper tissue. The bores cannot be cleaned properly with kerosene or solvent.

The usual advice is to make the engine pull, in bursts, as soon as possible after first starting it with new rings. I wouldn’t say “thrashing” is a good description of that.

Hi TT, I was making refrence to the previous comment.....


Everyone rides differently, I never keep my bikes reving low in a high gear (unless im on the motorway then it'll sit somewhere between 3500/4500 revs), I find this kind of riding is sufficient for running in. I have very good compression on both cylinders, the oil also takes forever to blacken. riding as previously mentioned the oil stank of fuel and the gas milage was pretty poor.

Worth having a read of the Hastings Cylinder bore refinishing guide Here.

It mentions that the cross hatch angles should be 45 degrees, the grit should be 220 to 280 and that they cylinders must be washed thoroughly afterwards as suggested. Difficult to tell but your cross hatch may be too shallow?

I guess the question is why only one cylinder is affected, some thoughts on this are:-
- maybe one piston was assembled with plenty of lube whilst the other was dry?
- cylinder honing different between cylinders, maybe wrong cross hatching?
- possible head gasket oil leak in one cylinder causing running in issues?

I would re hone the bores, use a dry assembly with the old rings and give it a hard run in.

I've remeasured more carefully today and found that 1" down from top the gap is .012" whilst at the bottom, .010". But the middle ring and oil ring had a whopping .024-.025" gaps. I also measured the bore 1" from the top and the piston front to back at about the mid point using telescoping gauge on the bore and then using my Mitutoyo 6" calipers. I get the piston at 3.006" and the bore at 3.010", so about .004" clearance. I don't have a bore gauge nor a 3-4" mic, so that's as close as I can get.

The bike has original BSA air filters and there's no smell of gas in the oil. Oil was new, less than 300 miles now. It's always possible the oil tank did not get cleaned as thoroughly as it should have, but the oil looks clean. However, the oil that gets deposited on the floor after a run looks dirty but could just be mixed with road grime and then runs off when I park it

I'm taking a ride up to Wolfville today to pick up some new rings, but no sure what brand. The ones I had were 1-piece oil ring, so not Hastings as I would prefer (3-piece oil rings).

Tom

P.S. I thought this forum was supposed to remember that I'm not a robot, but it doesn't seem to.

Re: Robot, might have something to do with your internet cookies....

Only other consideration is were the rings fitted the right way up? Its possible that it might be sealing well enough to stop blow by of fuel getting past the rings but might just be allowing oil to pass one way.

Another ring option is to give Ed V a call, he is a supplier of Total Seal Rings, I have these on a set of his JE pistons. Never had any oil/fuel cross over contamination issues with them....

Another alternative is there is nothing wrong with your piston rings, Infact you have a very good ring seal and its highlighted a problem in your inlet valve guide (I had this when I first fitted the TS Rings, I thought it was poor ring seal but found it was a bad valve guide pulling oil in and causing it to smoke, after having K-liners fitted it solved the problem)

It looks to me somebody forgot to hone your right cylinder at all, but pistons don't show this blow by. They really look pristine, like they have a good seal with cylinders. This is why I'd check your valves and guides per Allan's advice. I think your head gasket was leaking on this cylinder too.

Valve guides are a good call, always worth a check. Depending on the guides used these are sometimes very short lived, before I heard of Kibblewhite I was very wary of " Bronze" guides , they all seemed to be made of a soft rapid wear material, I much preferred iron guides, now running K guides and fairly pleased so far.

Every old A65 head/ valves I have had in my hands had valves that were worn fore and aft, no sign of valve rotation whatsoever, the guides wear the same to match.

Ive run both sorts of oil ring no preference.

Although large at 24/ 25 thou end gaps , motors will run fine like this without major issues, I dont think thats the smoking gun. i would be more concerned about the 10 thou gap top ring, if it has worn at all then that gap was too tight when fitted .

Current thoughts on piston ring end gaps are that its better to have a larger gap on the 2nd ring , 1-2 thou ,more than the top, learned it here from John Healy who had a very interesting link about how this was found.
It might be a good idea to give the head a wee skim to clear up the divot, you dont have to nix it completely if you win back 50 % of the divot with a 5 thou cut that would be a whole lot better., and if possible have the head bolt holes on the top side spot faced, the inner five are easy enough , the outer 4 are a bit more tricky. Solid Cu is a better bet than composite for A65 head gaskets.

4 thou piston clearance at the bottom seem about right , if the top ring only closes 3 thou from bottom to top then the wear is not huge ( 3 thou on the circumference is about 1 thou on the diameter), hopefully a good 45 degree refresh with the right stones will remove most of the wear marks, at 60 thou over you dont have many other options unless you sleeve the bores and start again.

There is a lot of carbon build up in both combustion chambers for a 300 mile engine

That's right but no burnt oil on the piston's sides at all. This is why I think guides are a culprit.

Looking closely at the pics again (and those are all we have to go on), for just 300 miles of use, both pistons have a lot of vertical scoring.
Some of those scores are really quite deep. This accords with the vertical scoring clearly evident in the smoother right bore (so easy to see) but I think similar vertical scoring is also present in the left bore (just masked by the rough honing).
As you know, this is indicative of honing grit remaining in the bores.

However, I find it hard to believe that both of those bores were honed in the same way. I'd doubt that the right bore was honed at all. If so, I'm thinking why has so much coarse grit entered the un-honed bore so soon after new build?
Of course some grit from the left bore would be dragged down, to be hurled about in the crankcase maelstrom, to find its way up between the right piston/bore.
Much of the grit would join the general oil circulation, to do its grinding mission on the rest of the engine, unless/until caught by a decent filter - not a pleasant thought. Was an oil filter in circuit?

Again depending on the pics, the top rings appear to be of a different material to the 2nd rings, and can you see how rough the surfaces of the 2 top rings on the left piston seem to be?

I return to your original pics of the bores/honing pattern. It may be just the pic, but the honing pattern in the left bore appears very crude and not what I would consider correct. Is it possible to show that more clearly?

At 300 miles only the left piston shows evidence of blowby, with minor staining of the land above the top ring (blowby to me is combustion gas passing to the crankcase).

However the head does show some indications of oil passing the rings to the right bore, the clean area suggests detonation (or maybe advanced timing) on that side.

In 3 hundred miles how many cold starts? could account for carbon, ticklers ( every time you tickle that carb till the gjuice runs out , thats washing oil off the bore) and worn needle jets who knows , , most folk run conservatively over jetted, if oil gets in as well . It couldnt have been too bad the exh v/vs are close in burn temp. To me its a dirty build with a leaky head gasket( seen worse ).
You should be able to eat your dinner with engine components on assembly, fog the air , put up dust sheets, warn the people around, add extra lighting, your preferred tunes, the full bhuna.

My personal opinion is the bore was not cleaned properly before assembly. While both bores show signs of striations left over from bits of the honing stone, I shouldn't have to explain that the right bore is by far the worst.

There is no tell tail signs that there wasn't enough piston clearance. Actually it looks like they had plenty of clearance. By the way, you measure the clearance on those pistons 1 to 2 mm up from the bottom of the skirt.

It wouldn't matter what the ring gap was. From what can be seen in the picture the contact face of the right hand set of rings are "toast".

Change the oil. Drain the sump. Clean up the pistons.

Get someone to hone the cylinder with a 180 grit stone (MAX 220). Get the cross hatch as close to 45° as possible. Then wash the cylinder in HOT SOAPY WATER. When you think it is clean do it for another ten minutes, no twenty. YOU CANNOT GET IT TOO CLEAN. AND NO, SOLVENTS WILL NOT DO THE JOB THAT HOT SOAPY WATER DOES!!!

You want a lightly oiled lint free white rag to come out as white as it was before you started!!!!!

The break in process REQUIRES that you build up the dynamic cylinder pressure - you want to do this by putting a moderate load on the rings during the first run through the gears. Do not let it idle!!!!!!! while you put on your helmet, gloves, etc. By putting a light load on the engine you increase the dynamic cylinder pressure which will push the rings out against the cylinder allowing them to seat ("break-in").

It is my opinion that Hastings has caused more grief in the Vintage British community with their universal 220-280 recommendation for honing. Yes, there are professionals have the expertise, equipment and who can hold the tolerance required, they are few and far between. That said, I believe the quality of the rings, or cylinder finish, had little, if anything, to do with this problem.

Another possibility is that one of the rings has a taper internally/externally and has been installed upside down, worth checking for any markings and also standing each ring on a flat surface and see if stands exactly 90 degrees from horizontal.