Ok, i have an idea.

[PolarisRider]

Well i have a 300ex. My friend has a piece of crap 250x motor that i could get parts from dirt cheap. I mean DIRT cheap. Does anyone know if i could use the side case and kicker assembly and put it on my 300? Switching the bottom end out is NOT an option. Too many parts are junk. Thank you

[rideredxc]

I've heard it can be done. I think there are some threads on here devoted to that already. Search around a bit you'll probably find them.