I have no idea what application his single ring piston was originally for, but mine is actually an early 90's RM125 piston (but 2mm overbore). And yes, the piston crown is about 1mm closer to the wrist pin than the stock NSR piston. The cylinders will have to be turned down on a lathe to accomodate this.

I dont think there is any single-ring piston on the market that perfectly matches the NSR piston specs. So if your engine has single-ring pistons, you really should take some measurements on the piston and cylinder and match them to the stock NSR specs to see where you are at. Then, you will have to figure out what application the single-ring piston was for in the first place.
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Paul Herr
'88 FZR4/GSXR/YZF Frankenbike
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