WR426 Engine Head & 500cc Piston

My intake valve let go and did quite a bit of damage. Yamaha wants $500 for a new head. Anyone have one used or know if there are any aftermarket companies that sell them. I am planing doing whatever can to increase the flow. I am also going to do the 450cc piston/jug in it but was wondering if anyone has done a 500cc setup. Some UK website shows a kit?

Any help would be greatly appreciated.

Your head can probably be repaired.

Contact Mike @ Edco.

Many people besides myself from this board have had good luck with him.


Dude, when my intake valve let loose it destroyed my head. $500 is a very good price. Powersportspro.com wants $610 for my head, which I gave. It was the best price going at the time. Here's the ball kicker, the head comes with no guides or valves. You have to buy that part as well. :) Yes, going up on cc's is easy and very much felt in the seat of the pants. I've had to do no mods on the carb to make it work, just less main jet. 2000WR400 to a 426. :D

Thanks for the info guys

When your valve let go how old was your bike? A friend of mine was riding mine when it went. He said it just went dead. I beat on it pretty good, so I dont know what he could of done. I think what happen was the intake valve let go then broke the exhause valve. Why it let go I have no idea? Did you oversize the valves when you replaced your head?

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