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Yz400f to a yz426f ?

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Ok guys I want to make my yz400 motor into a 426 motor do I have to just buy the piston and jug of do I have to get a crank to or more ??

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I believe it is direct bolt on conversion.

Piston,cylinder, head, if I remember right.

May do some checking the head maybe the same for both.

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Not quite direct.  The 426 cylinder will bolt on, but the wrist pin is a different size. 

 

Option one is to either use a 426 crank, or rebuild yours with a 426 rod, then use the 426 piston.

 

Option two is to use a piston from an '03-'05 YZ450F, which has the same size pin as the 400.

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If I used the 450 piston would I have to get a 450 jug

 

No: The 426 bore is the same as the 450, and if you use a 450 cylinder, you need a 450 head with it.  The 400/426 head will not work. 

 

 

And will my transmission and all that hold up to a 450

 

Probably not, but it won't be a 450 even with a 450 top end on it because the stroke will still be the same.  The displacement will be 426cc.

 

In any case, IMO, it's way more work than the old bike merits having done to it.

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