426 crank in a 400?

My WR400 has developed a rattle in the motor. I suspect it is a rod bearing, or so I've been told by some TT'ers.

Anyway, assuming I have to rebuild it, can I put a 426 crank and piston in the 400 motor assuming I rebore the cylinder?

A friend has a good 426 crank and rod.

Also, can you guys recommend a good engine rebuilder who can do a quick turnaround?


Eric Gorr, I would contact him about the piston and crank also, I'm pretty sure its the same stroke, would just need to be bored out to hanlde the larger piston. www.ericgorr.com

One of the problems with these motors is a nut coming loose on one of the internal drive gears in the motor (dont know exactly which one). This then allows the gear to rattle on the shaft key, with only a locking washer tab preventing the gear from loosening completely. I know of at least 2 motors that have had this horrible noise - sounds like the motor bottom end is about to self destruct.

Eric Gore, I have never been able to reach him or anyone in his shop by phone for quite a while. His web site now says he charges $5 minute for questions, have your mastercard ready. He further says he can't get parts to complete the motors he already has.

Any other recomendations for someone who might be intersted in doing the work?

I think the 426 stroke is a couple mm longer, but with the shorter rod I presume it should work fine. I just need someone to confirm it for me


Well when I built up my warrior 4 wheeler (don't hate me since I own atv's too) I ordered all of my stuff from white brothers. I would call them up. They have been working with these bikes for a long time. www.whitebros.com

The calls didn't cost me anything. And they answered my piston,cam,valve's,springs ect questions.

I think thumper racing might be able to help you too, but i've never dealt with them. don't know there sight.

www.powroll.com is another good one, might wanna try them out. There labor prices seem pretty fair to me, and they've been around a long time.

Thanks for the advice.

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