head gasket troubles

[greg_gorrell]

my 400ex keeps blowing head gaskets. i have gone through like 5 now and im getting ready to replace it again. the past few times i have noticed the caps on the head studs being loose when i went to take off the head. the last time i put it together i put some medium strength thread locker on the caps and it just blew again. all time i have tightened them to the torque that ius given in both services manuals i have, which is 33ft lbs. so idk but the deal is now. i have never had this problem, usually i just put a drop of oil on the threads so they dont seize on me and put the cap on then tighten to 33ft lbs. if anyone has any suggestions, they would greatly be appreciated as im am getting very frustrated.

[Glamis400ex]

Any hi comp piston needs to be at 38 lbs. Look at getting some heavy duty studs as well.

[RiderTRX400ex]

what brand of headgasket are you using? head studs could be pulling out

[400exrider707]

Originally posted by RiderTRX400ex
what brand of headgasket are you using? head studs could be pulling out

exactly. When I rebuilt mine I used tusk top end gaskets and they went within a few hours of riding. Switched it over to a cometic thin gasket which was more money but it never blew again. Also the studs themselves are quite possibly pulling out. Also the head could possibly be warped too, might need it decked.

[400exrules]

yes, get some cometic thin gaskets before upgrading to HD studs or doing anything else.


ill be gettin my 99 400 bored to a 416 with a 10.8:1 piston soon, and im gonna keep the stock studs, and just use a cometic gasket and see how that does. i hope my studs dont pull. do yall think i should get HD studs? i cant really afford them...

[greg_gorrell]

sorry, i did fail to mention i have heavy duty head studs in it and also have went through 2 of the honda oem gaskets and this is the 3rd cometic gasket i believe. im trying to sell this and if its not gonna hold up for more than a few days im not gonna rip somebody off you know what i mean?

[swva400ex]

mines a std. bore 11:1 piston. i ride mine pretty hard and often.i have the k&s gasket. it is still holding up fine.i have heard alot about this though.kinda got me thinking

[GPracer2500]

Originally posted by greg_gorrell
sorry, i did fail to mention i have heavy duty head studs in it and also have went through 2 of the honda oem gaskets and this is the 3rd cometic gasket i believe. im trying to sell this and if its not gonna hold up for more than a few days im not gonna rip somebody off you know what i mean?

Might want to get the head and cylinder checked at a machine shop to be sure they are perfectly flat.

[RiderTRX400ex]

yea if your using good gaskets and you have HD studs, i dont know what else could be the problem other than a warped surface.. good luck!

[greg_gorrell]

yea i was gonna do that, but my main question is why would those head stud caps be comming loose?

[RiderTRX400ex]

yea that is odd... maybe your torque wrench is out of whack, try a different one just for the hell of it next time you put a new head gasket in .. good luck

[400exrider707]

Who installed the studs? I bet they're still pulling.

[DieselBoy]

threads/nut worn?

[86 Quad R]

i may be way off here but, would detonation cause the head nuts to become loose? i've seen it many times cause spark plugs to back out. i dunno, juss a thought. :confused:

[greg_gorrell]

i installed the over sized head studs last time this happed because a couple of the old studs were pulling out when i screwed the caps on. i checked the new ones and they are tight.

[400exrules]

will stock studs be ok on a 416 10.8:1 if they can hold 33lbs when you torque them?

i can afford the motor work and the piston right now, but i cant afford to get HD studs, and get them installed