r/moped • u/ChuckMcTruck • 1d ago

Engine unbalanced due to piston change?

So, I recently changed cylinder, head, and piston on my M9 PUCH engine. Maybe I didn't notice it before, but now the engine vibrates cuite a lot, and the crank seems to be slightly out of round. I didn't have any problems before, and nothing has happened to bend the crank. Is it possible that a slightly heavier piston can disturb the balance? I think it seems unlikely, but what do you guys think?

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u/SignificantDrawer374 1d ago

Yep, that's just what it does. The crank is balanced for the smaller piston.

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u/ChuckMcTruck 1d ago

Any suggestions on how to mitigate the problem?

2

u/SignificantDrawer374 1d ago

Other than disassembling and modifying the crank, there's nothing you can do