I have seen a few posts here asking about using the YFZ 450 cams in 400s/426s Well i am the ginny pig here and did it. I was not looking for big horsepower like the yz cams produce because here in texas we have alot of single track sand trails, Oh and did i mention we have alot of SAND here???????!!!!!!!!! So yz timing just causes more trouble than good for me. All i wanted was the newer Wr450 power which i believe to be very strong but smoother than the old 400/426s. Well i was supprised just how much power it has right off idle, Its a torque monster for sure. The auto decompressor was also a bonus but not a necessity since im kick start anyway and the decomp lever always works just fine. So the answer to your questions is yes it works well but it is equivelent to wr power not yz. I did some research and the hot cams part number is exactly the same for the YFZ450 and the Wr450. I know yamaha part numbers are different but this could be due to the decomp pin difference. Naturally you will have to reshim same as using the newer yzf cams because the base circle is just a little smaller than the old cams but this is not a big deal at all.