HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
boricua1

99 yz 400f top end rebuild

8 posts in this topic

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.

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites
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.

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites
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.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0