300 ex cylinder on 250 x

[minor70]

im putting a 300 ex cylinder on my 250 x and am hoping someone else has done this. what else do i need to change or is it a direct bolt on as i have been told.

[bwamos]

Well.. if you're jsut putting on the cylinder and head.. it's all identical except for a slightly different cam tuned for the longer stroke of the 300ex.

If you're not replacing the piston/crank you still have a 250x.

[minor70]

yes thats what i meant was i wanted to put in the longer connecting rod to make it a 300 . and was wondering if it would work

[beaubs]

They are the same with the execption of the breather port.

[minor70]

what do you mean by breather port. and do you mean that the rods are the same length or the crank diameter is the same. have you done this to your quad by chance

[bwamos]

To get the longer stroke you'd have to repace the bottom end. Not the top end.

The rod does not make the piston move further. The radius of the crank does.

[95SiDanO]

So a 250X head would directly bolt onto a 300ex motor?

[Sjorge450R]

yep

[95SiDanO]

What about a 250ex head?

[ss420ex]

that partially true about replacing the bottom end to see a difference in stroke.... but im pretty sure u can buy a connecting rod that has different specs to make it a longer stroke.... but yea, i agree. id replace the bottom end to see the difference......
speaking of bottom ends... anyone hav a 250x or 300ex bottom end in decent condition??? i blew a hole clear thru my bottom end by the front motormounts

[95SiDanO]

I got a second chance offer on ebay for a 250ex motor, missing the piston and camshaft for $110. You could check that out.

[witech]

A 250x and a 250ex are completely different engines.