This may be a dumb question but I was wondering what the best way or if there is a way, to turn my 250x into a 300? I was wondering if the top end would fit from a 300ex or not, seeing how most other parts are interchangable between the two bikes.
thanks

 

There is no difference in the topends of the 250X and 300EX

The 300EX gains it's "bigger" engine by using a stoker crankshaft. The crankshaft is a bit different in design than the 250X and will not work in the X.

You can get bigbore kits and stroker crankshafts from lots of different companies out there. Powroll is the most popular ones. They use a shrunken rod technique to your stock crankshaft assembly. It's less expensive than actually replacing the crankshaft with one that has a shorter made rod.

 

I have a 250x motor with one of powrolls 273 big bore kits in it and it ran great.

 

The 300ex has a different stroke. The bore is the same as the 250x. I think that the cases on the bottom end along with other stuff is different on the 300ex. You might be able to use a rod from a 300ex? I looked in to it last summer when i wanted to do it to my 250x.

 

Thanks guys for the info.