Need next size up on the piston? Maybe the sound you here is piston slap.
The top of your piston should have an A,B,C or D stamped in it.
My last rebuild I changed rings but not the piston, I have great compression, runs really nice, but makes one hell of a clatter due to piston slap............Yes I know my rings will wear out prematurely from it.
Much great Sherco Info. here