hmmm, not strictly true, indeed VHM do not list NSR250 pistons but to say they don't make any that fit? Well, that's another matter.

Maxim's Wiseco pistoned, VHM headed 300 revs like a 250 and makes better power than any other 300 I've seen, 10%+ up on what yours makes. How much of that is Wisco, how much is VHM, how much is difference between dyno's and how much is Mr.Matt's porting is another matter.

The stock 300 kit pistons are heavy ol' slugs, the Wiseco's have got to help both power and crank life to a degree but lighter engine parts tend to mean the engine can be tuned more rather than give a big improvement on their own.
This seems to be as near as you'll get to the kit you're after.
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