i was just wandering if a 300 ex motor would slide right into my 250x frame, with no problems?

 

Yes, it would.

Although, I don't know this for sure, but I think I have read that the 250x motor actually makes a little more horsepower than the 300 because of higher compression.

 

The 250x and the 300ex frames are identical. . .the only difference in the entire bike is the bigger bore which makes the motor into the 300. I put an atc 350x motor in my 250x frmae with minor modifications. But the 300 should slide right in. . no problems. Good luck! Let me know if you have any questions.