Head Gasket Procedure - wr426

Suspected blown head gasket/and or warped head after rebuilding this beast. She ran beautifully for a few hours and then died out. Not seized, just died at idle. Plug soaking wet in coolant. Did see a little weepage on head gasket near the head bolts on right side.

My bad, rebuilt tranny and didnt tighten head to spec. The bolts on the right side of head could be tightened about 1/2 a turn? Suspect head bolts under cam area loose too?

No coolant in oil.

Any advice on rebuilding the head again? Have a used yz426 head as back up if mine is warped. I learned my lesson and appreciate any procedure to follow.

That top end can be redone while mounted on frame, correct?

Yes, you can do it in the frame. I doubt you need to do anything more than replace the gasket. If you want to be extra sure, buy some Permatex 'Copper Coat'. Spray two coats on both sides (spray, wait 30 minutes, spray again) of the gasket 24 hours before assembly. Make sure the head and barrel gasket surfaces are surgically clean.

Thanks, can you share the torque specs and procedure?

Not certain it's the same for the 426 as the 450, but it should be:

Apply moly disulfide grease (moly assembly lube) to the threads and under the bolt head. Torque to 22 ft. lbs. Remove the bolts and re-apply moly grease. Torque to 14 ft. lbs then an additional 1/4 turn each, and then again an additional 1/4 turn each (a total of 1/2 turn past 14 ft lbs). Done :thumbsup:

Edited by bg10459

Thanks for the help. Can anyone confirm the torque specs on the head bolts. Also, how the heck am i to get a torque wrench on some of the bolts under the exhaust and under the carb????

The torque specs seems low.......??? Anybody help confirm please.

I already have a service manual, however it is over 1 hour drive away at the shop that is rebuilding my stator which is why i turned to this forum for help.

I ended up downloading a manual for $8 and all set, bike back together with the right torque and pattern.

If anyone needs to know, the main head bolts get fastened to 32 ft/lbs.....but tighten down in increments:

The 4 bolts get fastend as follows:

#1 stator side - rear

#2 clutch side - front

#3 stator side - front

#4 clutch side - rear

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