Modify yz 400 to 426

7 replies to this topic
  • don5154

Posted December 27, 2006 - 05:10 PM


Hi All
Just pulled my beloved yz400 down and would like to convert it to 426cc. I know from scearching the posts that a 426 cylinder, piston, rod and crank pin will interchange.
Does anyone if I can use a 426 crank instead of rebuilding the 400 crank?
Thanks for reading this.

  • PumpkinHumper

Posted December 27, 2006 - 06:54 PM


dont know if you can use the 426 crank but here is some more info on what you are looking to do


  • CRF100biker

Posted December 27, 2006 - 07:37 PM


Wow 440 cc's. Now if the bike were lighter and didn't have the manual decompression it'd still be competitive. For $550 that's probobly not a bad choice. I remember there was a 420 kit a while back.

  • yz454

Posted December 27, 2006 - 09:53 PM


Yes there was a 420 or lets say 417,Some piston maf mite sill have some a round but ,why the 426 rod ,is because the 400 pin size was to small and would break.I had one of the first 450 kits in 98.

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  • don5154

Posted December 27, 2006 - 10:35 PM


Thanks Guys

The stock cylinder has a score mark. The shop manual recommends replacing it and the piston. I might as well go with the 426 mod for the stronger rist pin. The cost is about the same for a 426 rod, bearing, pin and labor as the new 426 crank assembly IF it it will fit. The right side of the 426 crank has a different part number.

  • brucifer

Posted December 28, 2006 - 05:04 PM


I think if you check you will find the 450 and the 400 use the same size piston pin.

I haven't started the motor yet but I have assembled a 400 with a 450 crank and a 426 cylinder and a 450 piston. Every thing turns over but I need to clearence everything and reclean the parts before I start it. And it has a 450 trans in it also. ?started? is that proper english? The 6mm bolt on the camchain side if the cylinder does not match the case. I will have to weld something here!

  • yz454

Posted December 28, 2006 - 08:58 PM


Call powroll they can answer all your ? One thing you will find is the cam chain sprocket on the crank is wore out.

  • don5154

Posted December 29, 2006 - 12:09 AM


Keep us informed how the 400 to 450 mod goes. You are very brave!!

Just learned that 426 crank will not fit 400 right side case.

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