250X head and cylinders same as 300EX?

[quadfamily]

I have a spare 250X head and I wanted to know if it is interchangeable with my 300EX head. I want to send it out and have it ported now so my quad will not be down for too long. What about the cylinders? Are they the same? I could have the 250X cylinder bored and ready to go if it will fit the 300EX engine. Thanks for any help!

[hondardr4life]

Yep, they are exactly the same, the only difference from a 250X motor to a 300ex motor is e-start and a stroked crank, the 250X head should sit right on there.

Please someone correct me if I'm wrong, but I am almost 100% sure they they are intercgangable.

[quadfamily]

anything different with the decompressor? Will the 300EX cam go into that head? I just need to be 100% sure before I invest money into it.

[2muchquad]

yes the 300ex cam will go into the head,i too have a 250x topend that im gonna have bored for my 300ex:)

[quadfamily]

Cool. What overbore are you going with, another 330? I was thinking of .080" over or possibly a 330 kit. Cases need to be machined for the 330 though. That would be ok though because I want to go through the bottom end anyway. Either way I want to go with 11.0:1 or 10.75:1 because I want to be able to use pump gas.

[2muchquad]

i only think some of the 330 kits require case machining,not positive.i will probably do 80 over on my spare cylinder,when that wears maybe a big bore.

[hondardr4life]

I didn't need to have the cases machined on mine to put in my 330, all they had to do was re sleeve and bore the cylinder. For a 350 kit, you need the cases machined.

[roostin_dale]

Originally posted by quadfamily
Cool. What overbore are you going with, another 330? I was thinking of .080" over or possibly a 330 kit. Cases need to be machined for the 330 though. That would be ok though because I want to go through the bottom end anyway. Either way I want to go with 11.0:1 or 10.75:1 because I want to be able to use pump gas.

If you go 330 or even a .80 you need to use a 12:1 or 13:1 to get more usable power...I had a 13:1 with my .80 bore..

EDIT: 11;1 will be fine though, just not as much power..

[2muchquad]

who makes a 13 to 1 piston for the 300ex?i know wiseco makes a 12 to 1 for the 250x

[hondardr4life]

If you go above 11.1, you will need to run race gas, and get an HD rod. So i personally don't reccomend going over 11.1