Difference in YZ/WR cylinders???

My buddy has an 06 YZ450f with an Athena big bore on it. He is selling it, but asked me if i want to swap cylinders from my 06 WR450. Are the cylinders interchangeable. Is the stroke the same on both bikes. I have always been under the assumption that the engines are the same, but different trannies.

Anybody??? Somebody has to know if there is a difference. Come on, this is TT

The 06 YZ had a completely redesigned engine with internal oil passages to the head (the 03-05 YZ's had an external oil line to the head). The WR didn't get the new engine until 07, so I do not believe that cylinder will work on your bike.

If its any help, I have an std '06 YZF cylinder on my '05 WR motor.

All the bolts line up, but the threads for the two bolts on the cam chain side are on the cylinder for the 06 version, with threads on the 05 head. So I just dont run any bolts there, no problems with leakage so its all good !

I also seem to remember chamfering the other side to clear the cases, but only by a couple of mill.

The water pump transfer is also machined shallower on the 06 cylinder, so I machined a new shorter o ring sleeve to suit.

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