I have heard alot of people say that a 300ex jug will fit on the 250X motor does anyone know forsure

 

Hmmm. Well, the bores are the same but the stroke on the 300 is longer. The part numbers are different from Honda. I guess it depends if the extra length of the stroke is at the bottom or top and that should be easy to check. Just measure the length of the jug. Are you planning to make the 250 a 300 or do you just want a new jug for the 250?