yz400 to 426 conversion

5 replies to this topic
  • allthrillzz400f

Posted January 21, 2006 - 08:18 PM


I have a 1998 yz400f and wouldn't mind having a bigger bike, I have a good friend with a wrecked 01 yz426f with an unharmed motor. Does anybody have any input on how hard it would be to convert the engine to my bike? :thumbsup:

  • 1rkcooper

Posted January 21, 2006 - 10:06 PM


Pull your motor out and put his in. I think everything should bolt up and line up but check to be sure. Give it a try one Sunday afternoon when the weather is really crappy.

  • DigilubeJay

Posted January 24, 2006 - 02:11 AM


I don't think the motor will bolt right in.
What you can do, and will be glad you did, is to take the 426 jug and have a 444 kit put in your motor. Some Kibblewhite valves and springs, and a little port work, and you can have a bike that makes more HP and torque than a new 450.
The 426 jug will mount up to the 400.
Eric Gorr's Forward Motion, Co. are experts at this procedure.

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  • 0042678

Posted January 24, 2006 - 08:24 AM


You should get his suspension to while your at it, assuming it will work. In other words just swap frames. Just a thought. :thumbsup:

  • Shwantz34

Posted January 24, 2006 - 07:09 PM


I have 2 YZ-426. A real one 2000, and my other one is a 400 1998 with a 426 motor. Have no fear, everything fit right there, no pain at all. You will have to make some litle jetting change maybe ( i sugest you to have is 426 carb they work better than the one on the 400) . All the rest air box ,pipe etc everathing will fit. On my 2000 ( 426) i had a bad luck last year ( my chain broke the motor base and i replace it with a 400 base they fit exactly the same.So have fun.

  • allthrillzz400f

Posted January 24, 2006 - 07:24 PM


Thanks for all the help i think i'll take the advice and put the motor in. Maybe mod it a little in the process. :thumbsup:

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