Well, some people drop a 4 stroke 450 Honda into the Aprilia 50 or Honda 125 frames. That's about the only way you're gonna get 40+ rwhp. My Aprilia RSR125 makes 42.5 rwhp, but it is a race bike and not streetable at all. No 125 or 150cc street bike is gonna give you 40hp without spending tens of thousands of dollars in development and parts. I mean, does the NSR150 even have a power jet carb or a power valve cylinder? It's the same problem as trying to get 80+ rwhp from our NSR250s. It isn't likely gonna happen.

My 2 cents,

Joel
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1994 MC28 Rothman
TSR250 AC28M