I am getting ready to rebuild a 250x. I have access to a good '05 crank. Will these two cranks interchange, I have read somewhere that the 300 uses a bigger crank bearing. I hope this will give me a easy way to get a bit more stroke out of my 250. If it will interchange without any mods, do I also need to use the 300 counterweight?

 

I doubt they will interchange since the 300 has a longer stroke.

 

plus the 300ex is electric start where the 250x is kick start

 

i dont believe they interchange. check out poweroll.com and they can make your 250 better!