250r BOTTOM END with 300ex TOP END

[ss420ex]

just checking... i hurd that the 250r bottom end is compatible with a 300ex top emd... i was wondering if thats correct... and if so, will the motor mounts and sprockets match up.
can any one help me out with sum info??
thanks!

[MossboysRacing]

yes and no. A 300ex top end will fit on a 250x bottom end. It will not fit on a 250r bottom end. 250r 2-stoke is way different than the 250x four-stroke

[ss420ex]

yea, there was a little confusion on the 250r n 250x.... gotthem mixed up. im almost positive that im gunna need a 250x wiring harness. anything else that ya can think of that ill need?

and will the motor mounts and sprockets match up without fabrication?

[MossboysRacing]

what kind of parts do you have from each machine ??? the only difference in the motors is the crank and flywheel... the 300ex wiring has a lot of added crap for the electric start. :) what frame are you putting this in ???

[ss420ex]

i hav a complete 1996 or 1997, 300ex... i cracked my bottom end wide open and dont wana waste the time rebuilding it... so im throwing out my old bottom end, and im going to find a 250x bottom end... change it up a little... so since id be using the 250x bottom end, id have to use the 250x wiring..correct?
my question is will everyting work without fabrication? and since its a different crank, should i re-jet my carb to a different spec?
and ofcourse, will this make it gain power, or lose power? or be about the same?