Modify yz 400 to 426

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.

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.

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.

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.

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!

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

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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