Valve Guide Replacement??

[slow-poke]

How hard is it to replace the Valve Guides on a YZ450F?

Are the Valve Guides pressed in?

Thanks,

[2grimjim]

Yes the valve guides are presed in. The head must first be heated to 300 degrees F and a piloted punch used to drive the guides out. The new guides can be chilled in liquid nitrogen or dry ice/acetone before installing to make installation easier. The guide bores (in the head) need to be measured first to see if oversize guides are necessary. There needs to be at least .001" interfearance fit for the guides to be properly retained.

After the new guides are pressed in, they need to be reamed or honed to the finished diameter for proper clearance with the valve stem.

This is a process best left to a competant machine shop.

[grayracer513]

After the new guides are pressed in, they need to be reamed or honed to the finished diameter for proper clearance with the valve stem....

After which the seats must be recut to ensure they are centered on the valve guides.

+1 on the machine shop.

Valve guides suffer very little wear in a YZF. Be sure you really need them.

[slow-poke]

Thanks for the replies, I will take it to the machine shop. It my uncles bike I am working on, all three intake valves are bent so I think it would be best to replace the valve guides.

[grayracer513]

all three intake valves are bent so I think it would be best to replace the valve guides.

That answers the question ?