1joel1 wrote: All NSR250s use the same motor iirc.Joel

Not even close! The MC16 is different to the MC18, which is different to the MC21. The 28 is quite a bit like a 21, but uses different carbs, flywheel and different port timing.

A lot of the parts are interchangable across the whole NSR lifespan, but sometimes you need to swap several parts over at once to make things work.
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball