250x

[1_fast_300ex]

I just got a Honda 250x, and the people I got it from left the valve cover off and the valves and springs rusted. I was wondering If a 300ex Head would fit a 250x Cylinder?
The cylinder is good and the crank is good, but I'm going to bore it anyway. If I was too bore it .080 over, Would i need to go to a bigger cam? Like a stage 2 hot cam? or if the 300ex head does fit, Would the 300ex cam be big enough?
I might race round track with this four stroke, then again I might sell it, If I can't can't enough power out of it. I know I should race a 400ex with a big bore kit, but the 250x was give to me.

Thanks.

[kuba1506]

I think they are identical motors except for the kick start. so i think a 300ex head would fit on it. about the came i am not sure im not big into 4 strokes so i dont really know.

[bradley300]

the stroke is also shorter on a 250x. bu yes, the heads will interchange. you woldnt NEED to go to a bigger cam, but you wont get the full hp. out of the bore job without it. i suggest going for a big bore 330 kit (its a 350kit in a 300ex) and have it ported and use a 400ex carb

[300ex73]

I'm pretty sure the head will fit, there's only a few differences, besides the obvious, on the 2 motors.

The 250X has a shorter stroke to the motor(57.3 on the 250x, 65.5 on the 300ex). Idk how much money you're willing to spend to make it faster, but my local engine builder says the first best thing to do is to have a good porting job done on the head. If it were me, I'd get the 300ex crank and rod put in, use a 300 cylinder jug and have it bored to a 297(stock the 300ex is a 282cc, the 250x is a 246cc), throw in the Wiseco 11:1 piston, have the head ported, toss in a good cam, and swap the carb.

Might be hard to kick over, but with the lack of weight from the battery and starter, plus whatever other weight you can shave, it'd definitely be pretty fast.

[1_fast_300ex]

Thanks guys, it was for a friend. He e mailed me and i wasnt sure so i posted it on here. Again thanks.

[riggsracing]

i know it will b/c i had a 250x witha 300ex head. the only thing that sucked was no compression release