YZ head on WR???

I am assembling a spare motor for my 03 wr450, just picking up parts where I can!

So far I have a new set of crank cases and a new "complete crank"

I can get hold of an 04 YZ450 complete head for the right price, and was wondering if there was any reason why I couldn't fit it to the WR!!!

Yes. It should mount up as far as I'm concerned. I was looking at doing the same mod to my bike. I think it will add a little extra punch too because the porting is a little different. The only problem you may encounter would be the electric start. The electric start is a bit finicky when combined with a YZ exhaust cam, so people have been suggesting Hotcams to cure the problem, or buy a WR exhaust cam.

Part numbers are the same for a bare WR head and bare YZ head, meaning ports, compression, etc are the same as well. Will fit as it's the same part. YZ cam timing will give you different power than the WR, but I don't know if it will work with e-start...I believe it will, but not sure. I know it has been documented here in other posts, so search away...

So the heads will interchange just fine, but how about cylinders? Are they compatible?

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