I stripped the mc16 engine today for some more tuning and a bit of maintenance. Once I'd lifted the heads off I was greeted with some very odd piston damage, so I took them out for closer inspection:







All in the same spot, just above the ring peg. Really weird for them both to have gone, possibly a fault with the piston?

Any ideas?
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More **** two strokes than you can shake a **** stick at.

Weren't fitted backwards were they?
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MC21SP Plaything
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GTS1000 oddball

Of course not... (I do check about 5 times when building engines..
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More **** two strokes than you can shake a **** stick at.

have the pegs actually left the building, Paul? Never seen anything quite like it, but did you measure the ring end gaps? Just wondering if they were a bit tight - making the ring ends mangle the peg?

Lucky you caught it when you did really though as those rings would have surely inched round 'til they managed to snag an end in a port...

I had exactly the same burn on my top cylinder piston last year. I put it down to the following:
I crashed in practice and damaged my gear linkage, leaving me with no 5th and 6th gear.
I had badly worn rings.
I was running a tight squish band for short circuit track.
I had to over-rev in 4th to try to keep up.
I think it was down to a type of detonation where the hot gas finds a way through the easiest passage (the ring gap) and keeps burning away in that specific point.
Did you have anything like this at any time recently?
It's a theory, but I don't know for sure. Welcome to the twilight zone!

as the picture suggests, it s only the top ring on both pistons. seems odd they are both equally damaged the same way. looks like the ring peg has come thru on both of em
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thats what happened to mine on the rear cylinder , but the ring spun round and snagged in the exhaust port , on closer inspection the ring peg had gone , i put it down to a dodgy piston

Thinking about it, possibly ring gaps too tight. But odd how they have both gone unless its a problem with the pistons? Bit odd as they are fairly new..

New ones on order!
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More **** two strokes than you can shake a **** stick at.

seems odd theres no damage to the second ring, again, on both pistons
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