Does any one know if a 300ex cylinder just the cylinder can fit on the 250x?? the engines are the exact same as far as i know except for eletric start and a longer stroke and little bigger bore.... if the cylinder fits i will put it on my 250x and put the valve train of the 250x back on it... then i will bore that out and then get my botom end cut so the piston will fit in it... well then add the crank i already have waiting to stick in.. 12.5mm... thanks for the help...

 

you asked if it would just "fit in" then said you were going to bore it out ?
I thought they had the same block just the bore size was diff.
So you should be able to bore the block and be in business.

 

figured it out.. there the exact same can be bored the same.. the only difference is the 300ex has a longer stroke.. making it a 280 something... So i didnt waist my time.. I already have an 80mm big bore in my bike.. but i thought i could get a bigger cylinder and go bigger on that bore...