400 to 426 top end swap

6 replies to this topic
  • sully16

Posted July 16, 2005 - 08:29 AM


Hey guys, does anyone know if you can bolt on a 2001 426 cylinder & head onto a 1999 400 bottom end? Are there any changes that need to be done, is it even possible? will the 99 carb still work with the 01 426 head? I took out my top end (99 400) and found someone parting out a top end from the 01 426. :applause:

  • Hick

Posted July 16, 2005 - 11:46 AM


Somebody else posted that the 400 head has an passage for the hot start, whereas the 426 hot start was integral to the carb.

In short I don't know if your 400's hot start will operate w/ the 426 head. Other than that the 426 carb is, I believe, oriented a bit differently, but it may work otherwise.

Also, the 426 piston will not fit on the 400 rod.

Hope this helps.

  • sully16

Posted July 16, 2005 - 11:56 AM


Thanks Hick, it does help. I will look into those items further.
Anyone else know of other potential problems?

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  • RCannon

Posted July 16, 2005 - 04:06 PM


I remember hearing talk of the wrist pin being a different size. If this is so, the rod is probaly different as well.

  • BergRyder

Posted July 16, 2005 - 06:08 PM


One easy way to look at the parts differences is on the Yamaha of Troy parts microfiche,
Look at the parts and part numbers of the model years that you are trying to swap, also look at the photos and diagrams in the Clymer workshop manual.
But yeah, your best resource will be someone who has actually done it.

  • sully16

Posted July 16, 2005 - 06:53 PM


Thanks BergRider, I have since gone to 'bikebandit.com' and checked their part drawings, they are also quite good with associated part numbers. It looks like there are quite a bit of differences. I may just end up parting out the bike. I have a potential deal going on a 2003 KLX400 at a local dealership here, should know on Monday what they want for it with my other bike in trade (not the broken YZF).

Thanks everyone for their suggestions and help, it sure is nice to have such a good site to come and find out what others have gone through to help make the decisions a little easier. :applause:

  • ex_junkie

Posted July 18, 2005 - 03:44 PM


U can bolt the 426 topend on the 400 bottom end. Thing is u have to use the 426 rode on the 400s crank. THe small end of the 426 rod is different. But the big end is the same.

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