Piston rings

[barney 66]

Morning all,
Anybody got any idea why both top rings on front and rear cylinder would be broke on my 1976 31/2 Strada? it’s has been stood 20 odd years and there is signs of light rust having been in there so my thought is top ring hitting agains rust, any thoughts please ?

Thanks barney

[MickeyMoto]

Did you put oil down the plug hole before turning over the engine? Might find the top rings starting to seize in the rust.

[barney 66]

Thanks for the reply, I did do that, and I dont remember it being stuck, it could have all happened prior to Dad buying it in 96 as Dad would have only pottered about on it.
Either I’m going to measure and hone cylinders see how they clean up, I can’t see any marks on the piston top to say what size they are if there standard or oversize, anybody know what piston and bore measurements are please ?

Thanks barney

[dunk 1]

both of mine went as well, not long after I got it, the bores were clean. The engine went to NLM for a check over the heads and barrels and they could nit give a specific reason either.
Duncan

[barney 66]

Thanks for the reply, had yours stood about as well or not ?

[dunk 1]

I'm not sure if it was stood but certainly had running issues which needed to be resolved so it is possible as it couldn't have gone far - although there was no sign of any corrosion in the barrels.
I presume the ring had gone on one cylinder first as it was using some oil, then when the second cylinder went it really threw it out - all over the back wheel.
All the lower rings were fine and keep in mind this happened a long time and many miles ago (I would have to check to be precise) with no recurrence and nothing else changed so it seems it could be just the rings have a finite lifespan?
Thanks Duncan

[barney 66]

Yes it’s hard to know, I have spoken to a few people now & nobody has come up with a clear reason, looks like mine have been broken a while by the blow by on them.
Strange thing compression was 140 ish on both cylinders good starter hot or cold went well even with broken top ring on both cylinders and second ring had 0.8mm gap in it, the thing that made me look properly was after 120 mile the oil had gone from max to just over halfway to the min and some misting on rear wheel rim

Thanks barney