a friend of mine has a kx 500 powered mojave.it's a handful to ride becaue of the short wheelbase.but it rips non the less.
there is enough room in the mojave chassis to put in any engine you want.so find a good motor and throw it in there.
another real popular setup around here anyway is putting in the ninja ex 500 twin motors.those things kick butt in the mojave chassis. and don't worry about the from it's plenty strong enough to handle whatevr you put in it.as long as it's done right. good luck.

 

Killerkx327, How are the vibrations on that kx 500 mojave, They must be pretty bad??