I'm not sure that change to the rear will improve the handling any, as a 190 is way too big for a little 250, but I'm sure it'd look awesome!
I don't know that the RS pipes will fit on an NSR, and most NSR pipes are based on the RS pipes anyway. Have your ports altered to match the RS, and swap to the RS single ring pistons. Ditch the airbox and you'll be good for a heap of top end power...
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball
