[Geeto67]

Personally I am a big fan of the old kx250 motor. 10:1 compression, water cooled, 45.5 peak hp, dead nuts reliable, and a nice powerband. A year old one with new parts should cost you $500, less for a couple of years old. The motor is tiny so fitment isn't going to be a problem.

If you want to get really crazy, start hanging around the snowmobile guys and see if one of them has a chain drive motor laying about. I think artic cat has an 800cc parallel twin two stroke that should whip on anything if you can put it in a bike frame.

 

[Geeto67]

quote:

Ya know, a while back a guy was selling a KX250 powered RZ350 racebike. Neat idea, ran it in the WERA singles class. Hmmm... I have a roller RZ350... What years did they make the KX250? Wonder if it'd be legal for the USCRA singles and F2 classes. Think the cuttoff on F2 is 1984 or 85.

Yeah, like I need another project.

quote:
If you want to get really crazy, start hanging around the snowmobile guys and see if one of them has a chain drive motor laying about. I think artic cat has an 800cc parallel twin two stroke that should whip on anything if you can put it in a bike frame.

with a auto clutch? That would be... interesting.

The first year of the kx250 was 1985, I think. There have been several generation changes since then but even the '85 motors were strong (a buddy of mine had one, loved that bike).

I wanted to put one in a derbi gpr 50, but I didn't have the scratch to buy the roller from vespa soho at the time. Besides, If I do one now I want it to be street legal. 45.5hp + 224lbs = 4.9 lbs per hp, or roughly the power to weight ratio of a nextel cup car. Formula one cars have power to weight ratios of 3 lbs per hp. Now picture it with some tannermatic carbon fairings and things really start to get interesting....

I saw recently a few bikes with artic cat engines, and most seem to use a HD primary and gearbox.