would a xr600 motor fit on a 400ex motor ? I was at my dealer today and was looking at a xr600r's motor and the head looked to be about the same size and shape as my 400ex's head.... do you think i could pop on a xr600 head with xr600 piston,rod,etc...and put heavy duty presure plates on, would it work ??

 

Dream on dude.

 

For enough cash and time, you can do almost anything you want. It sounds like you are interested in putting the cylinder and the head on the 400's bottom end. I say this because you mentioned using the 600's piston. Basically, you would need to have your engine case machind to allow the bigger cylinder to fit. The cylinder head and valvetrain cover both connect to the cylinder. Might also need a custom length timing chain.

Like I said, if you have the cash, I'm sure it could be done. Might be cheaper and easier to just find a complete XR600 engine and stuff it into your frame.

 

fitting in a complete engine would be way easier. BTW, you won't be able to just put pistons and everuthing unless 400 and 600 have the same stroke. If they don't you'll have to change crankshaft, crankcase...infinite job

 

No way to do it with out change the bottom end too (in other words a new engine). Yesterday we were installing my new IMS 440 kit, and we have a xr600 head next to us, I remember your post, so as soon as we took off my 400 top end, we try to fit the 600 top end on my bottom end, and is simple impossible, no way to do it without have a big machinery work on the bottom.