WR/YZ426 cylinder head differences

[launchzone]

What are the differences between the YZ/WR426 , YZ/WR450 cylinder heads?

Will the 426 head fit the 450?

Are the 450 cam chain & 450 cams compatible with a 426 head on a 450

info appreciated!

[grayracer513]

I don't think you'll have much luck with that one. The 450 head is considerably different than a 426. The cams are lower in the 450, and are set apart on different centers (which is why the timing marks don't line up when using the 450 cam in a 426). The chains are different lengths, and are of a different pitch. The pitch difference is very small, and causes no problem when the 426 chain is used on a 450 cam, but it might be different running the wrong chain on the crank sprocket.

The bolt pattern might also be different, but I'm not sure.

I see no advantage to using a 426 head on a 450 anyway. What were you thinking?

[launchzone]

I was just wondering because I want to get a spare head and have it ported and assembled with stainless steel valves. If the 426 heads were the same, there will be more heads on the market (Ebay)! Presently, my WR450 runs strong with 50 RWHP, but I'm building a spare stroked crank with ceramic bearings, new cylinder with OEM 95mm piston and eventually a ported head with SS valves for reliability (looking for 55-60HP on the next rebuild).