99 yz 400f top end rebuild

I have a 99 yz 400f took the top end off due to a base gasket leak come to find out that wasnt the only thing wrong i a broken piston ring and piston slap and a damaged head from the piston slap and excessive wear were the cams sit. NOW MY QUESTION IS would i be able to stock bore 426 cylinder and piston with stock 400 crank and heads or would i have to chenge all that???:bonk: anything helps. Thanks.

From my understanding the cylinder will bolt right on. But you can not use the 426 piston with the 400 connecting rod due to the different piston pin diameter.

From my understanding the cylinder will bolt right on. But you can not use the 426 piston with the 400 connecting rod due to the different piston pin diameter.
That part is true, but you can have the crank rebuilt with the 426 rod to get around it.

Sounds like too much work .... imp keep it stock. It will probably run longer.

What about the head would i have to change anything up there as in valves or cams or anything else? or would i have to buy a 426 head also

I believe the 400 and 426 heads will interchange.

What about the head would i have to change anything up there as in valves or cams or anything else? or would i have to buy a 426 head also

I have 3 buddys who all converted yz400 motors into 426cc and they say all you need is a 426 cylinder, piston and rod.

As for timing chains Wat would u say is the best?

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