As long as the exhaust port was not widened into them ,one of my saw has fingers and the piston has to be in backwards because of what likely happened here .Would it have caught a ring if the piston was put in backwards?
not me, I wouldn't trust myself to do port work like that. I bought it with another one as parts saws.did you do the porting?
dang that hurts
I also couldn't really see anywhere that the ring dug into the cylinder, that is why I was asking. It seemed the most likely scenario to me that the ring end got caught. I like the idea of putting another piston in and seeing what happens. But maybe backwards if the ends clear the exhaust port.Maybe, but I'm not seeing where the ring dug into anything. Maybe its my old eyes and there is, I don't see it. Of course if there is evidence then obviously the answer is yes, those finger ports let the ring ends float and eventually fail. Even if there wasn't a catastrophic "dig" and it was a cyclical failure I would expect to see some evidence in or around the finger port if the rings were moving out of their grooves & being forced back in against their will... Failure Might be cause be a "flutter" because of change in bearing surface, piston to cylinder wall clearance, or something else. Could have been a marginal piston....lots of things. Maybe it didn't like the new RPM's allowed by the greater transfer port area so while not directly caused by the shape, the resultant dynamics killed it. Best way to find out??? Stuff another piston in there and run it... Either way if it fails again you have to put another top end on it! Might as well test the theory and get some more use out of that one...
I have to confess to NOT liking anything that would let the open ends of the rings "float" unsupported. Common sense flags that as a way to wreck a saw. Are there any single ring piston options with a more favorable pin location? How wide is the exhaust port? What would happen if you ran the piston backwards should you see evidence of "trauma" around where the ends of those rings ride in the bore and still want to run that cylinder. Would those pins ride on the cylinder wall vs. across the exhaust port?
Can't answer that, don't know who built it or if it was ever replaced.The piston would typically be installed backwards or the pins otherwise moved on a build like that. Was the piston replaced by someone other than the builder?
I think it is a normal size transfer, it looks like the only porting done was the fingers and some weird groove by the exhaust. Maybe the uppers were raised, but not sure.Hard to tell if its just the lighting or what, but almost looks like a little shiny spot on transfer port roof, that looks like a more likely spot for a ring end to hang but hard to tell wothout being roght there to be able to line it up. Im pretty novice when it comes port timing/mods but is that a normal sized transfer port? Seems very wide. Those fingers look very nice
That is in the exhaust port, have no idea what the point of it is.I a on a learning curve here, so I need to know if the teardrop opening is on the exhaust side or intake side. I believe it is on the exhaust side, but not sure. Tom
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