Yzf400/426 Question

[TC426EX]

I have an opportunity to get a YZ400F engine for a good price from a friend out of his dirtbike. Is this motor the same as the 426 and 450 with a different bore, or is there alot different with the engines internally? Would I be able to get this 400 bored to a 440 or 450 and have basically the same engine as the new 450? If I got it I would be sending it to TC to do the works to it. Cam, bore, hi comp. piston, port+polish, you name it. I just want to know if its compatible and basically the same engine as the later 426 and 450 just with a smaller bore... Any help is appreciated...

[panteramatt]

Man, Ive been asking the same question.

[C41Xracer]

they are both the same, the 450 is the same in some ways and different in others.If its a good price id buy it

[racerx573]

The 400's, and 426's are almost the same in all ways, except the displacement. I am pretty sure you can use a 426 cylinder on a 400, but not the 450...not 100% sure on that though. I have heard horror stories of 426's bored to 440's having piston cracking problems. The 426 I just bought was put back to a 426 from 440 because of this... check www.thumpertalk.com and ask about the interchangable parts.

[C41Xracer]

racerx is right you can interchange 400 and 426 cylinders and all other parts.Ive also heard about the 440's having problems also