What does a broken ring sound like?

I decided to tear down my motor as a noise/vibration had developed that didn't sound good. I haven't gotten too far into it, but found the top timing side ring was broken in two. Other than that, things seem OK and I was wondering if the broken ring could be the issue.

Which makes me think to ask - can you get new rings (if so, how do you specify?) and can I reuse the circlips - or should I do I get new ones?

Thanks, David

Get new rings from Andover or your local supplier. They have to fit the pistons. Original bore ?

napanorton said:

and can I reuse the circlips - or should I do I get new ones?

Click to expand...

Never re use gudgeon pin circlips!

And whilst you’re at it, check you get the right ones. Meaning, check your pistons to see if they’re machined for square or round section circlips. Lots of pertinent info for you in other recent threads on this...

I have never heard any noise caused by a broken ring. It was likely broken during assembly.

And fast Eddie is right. Get new circlips.

The oversize should be stamped in the top of the piston. I should have rings and circlips.

comnoz said:

I have never heard any noise caused by a broken ring. It was likely broken during assembly.

And fast Eddie is right. Get new circlips.

The oversize should be stamped in the top of the piston. I should have rings and circlips.

Click to expand...

and avoid the current rings supplied with ‘Hepolite’ pistons!!

jan nelder said:

and avoid the current rings supplied with ‘Hepolite’ pistons!!

Click to expand...

I second that.

Never put a ring back in a piston with broken rings. The ring lands are probably blown out and new rings will just break again. Hepolite pistons have a problem with the ring lands opening up and when that happens it starts burning oil or the rings break or both. If you can get a .003 or .004" feeler gauge between the rings and the ring land - those pistons are junk.

Keep on tearing down and establish complete condition of the motor.

Timing chain and tensioner. Oil Pump and drive. Main bearings, big end bearings, sludge trap, rods, cam and bearings, followers, valves, valve guides, rockers and pins. Primary drive.

That should settle in your mind the right solutions. Why set yourself up for doing it twice?

Better to lose one riding season than two!

If the rings you buy are for the next bore oversize, you can usually file the gap to end up at about 12 thou of an inch. Even if the rings are nominally the right size for the bore, you should check the gap. If it is too tight, you can push the piston into the bore and have it lock up, particularly if there is a wear step. I once had to break a piston in an old bike, to get it out after it jammed in the bore.

acotrel said:

If the rings you buy are for the next bore oversize,

Click to expand...

Bad advice.

Rings have to be for the bore size you have.

If the land in the piston that carried the broken ring hasn't been hogged out, which you can check with a "good" ring from the other piston then you can purchase a ring set that is compatible with the pistons.

My experience with ring end gap is that the gaps are too small and that the rings have to be filed/ground to achieve the proper gap; each one needs to be checked. New circlips, no question. Good idea to check piston/skirt clearance in both bores and give the cylinders a light hone.

As Comnoz has mentioned often, best to fit the piston/ring assemblies from the bottom using your fingers. The ring compressors I have are great for making the egg part of egg-mcmuffins when fully closed and lightly oiled with butter or decent olive oil...

Best

If you are going to replace your rings, then the pistons will need some work as well. Better to just buy new pistons and rings etc as a set. Cheaper in the long run, but that's just the mechanic in me speaking..
Dereck

no, you cant there broken rings. never heard any of mine.

I still see bad advice being given on this forum. When will it cease?

You’d better be able to separate wheat from chafe when viewing this site.

I can. but some other poor sod might not.

Detonation can cause broken top rings ...So can a quickie ring job and not dealing with the wear ridge at the top...And as mentioned careless assembly...

Amen.

kerinorton said:

I still see bad advice being given on this forum. When will it cease?

Click to expand...

I doubt that misleading or bad advice will ever cease on this or any other forum, regardless of topic. The beauty of this social platform is that the correct advice lies in the numbers, but does require that the responses be distilled with a degree of judgement and skepticism; I find this intellectually appealing and even in the most off-base responses I don't get a sense of any malicious intent.

I will freely admit that some of the advice I have offered, or alluded to, may have missed the mark here or there, and I have taken my lumps; even in this thread; fortunately we are blessed with individuals that are quick to correct.

If I was the OP I would come away with the following:

1) Hone the barrel to remove the vertical score(s).
2) Measure the bore to determine if new pistons of the same dimensions are viable, over bore if not. Replace pistons in any event.
3) Check ring end gap, adjust as required.
4) Refit piston/ring assemblies from the bottom with fingers and use proper circlips.

The appeal of the Commando (other British motorcycles as well) is that they present me with an enjoyable, engaging challenge, if not I'd re-apply to medical school...

Best

Hillbilly Bike said:

Detonation can cause broken top rings ...So can a quickie ring job and not dealing with the wear ridge at the top...And as mentioned careless assembly...

Click to expand...

I agree, and check for wear in the piston ring groove. Fit a good ring into the piston groove and use a feeler gauge. I cant remember the spec, something around 0.002" to 0.0015". I'm sure the piston manufacturer will provide it. If the gap is too big the piston is scrap and ring will break again even if everything is put right.
As a kid I can remember the old motor engineers getting the piston grooves and matching rings re machined.

I shan't attempt advice. To me the broken ring implies only that I'm going to be doing at a minimum a hone job, two pistons/rings, thorough check of gudgeons/w new clips which are of proper fit, inspect valves/guides/seals, check head/cylinder surface seal area, proper head gasket, & myriad assorted tasks.... In other words I'm going to be busy.... While at it just as soon take care of those old wheel bearings, clutch, etc.
In for a penny and all that.... Patchwork gets nothing in the long run, except more patchwork on top of that. Believe me as I've been trying like hell to rid myself of evidence from 40 years ago. Fix it to where you have confidence when it starts.