[monty16v]

Rotax 257
250 single cylinder
pretty straightforward swap

 

[monty16v]

If you want to keep it Aprilia/Rotax Pegaso 650 motor fits quite nicely too.

Lazy big slug, better off with a 250
the 650s have the oil inside the frame as well

 

[monty16v]

I know they were used in supermono, does the motor differ in tune between the Aprilia/BMW/husaberg it's used in?

Obvs better to keep it 2-stroke, just throwing some right hand sprocket options out there

mostly the head, the aprilia has 5 valves
no extra power though
I dont think they even make 50bhp
and you would need to fabricate somewhere to hold the engine oil

 

[monty16v]

Im sure the heat from that exhaust is comfortable on the leg lol