blown head gasket

[12blaster34]

my 400ex is all stock but the head gasket keeps blowing. any idea what causes this to happen?

[Ruby Soho]

warped head if its not torqued properly

[nskukalek79]

i had the same problem with my head gasket blowing out and i tried everything...i got my head and cylinder checked to see if they were warped and they weren't, i tried a gasket sealant, and i blew 4 gaskets before i found the problem but i found that the threads were the studs go into the cylinder were stripped out and after about an hour of riding the compression would just lift my head up enough for it to leak. i had to buy a new cylinder but you might just be able to heli coil a hole if it is stripped out

[Chukkinsod]

Yup, I had to get mine heli coiled once already. I just blew my gasket again yesterday and have to see if I pulled them again. I'm runnin 12.5/1 compression on a 440 though....weird that a stock motor blew a gasket. I'd put another one in and see if it goes agin , maybe the head noth torqued properly. if you pulled the stud (heat) You can go with an HD stud, but if you pull those you are into a new cylinder. built 400 notorious for head gaskets blowin, some have luck others do not...

[nskukalek79]

well i just hace 11:1 compression on a .040 over piston but i put two heli coils in and they just pulled out but then i found out that the guy torqing my studs was making them 45ft/lbs and they are just supposed to be 33ft/lbs, so i think he started stripping the threads before i rode at all

[Pipeless416]

head studs can stretch over time too. being that yours is a 2000, you might have luck with replacing them.

[CK1999.400ex]

i had the same problem with my original 1999 jug after the second rebuild ... i replaced it with one that had not had the studs removed from it ,and just put my bored cylinder in the newer jug ,and put it back together and it was fine ... good luck with it how ever u deside to fix it ...

[AZ440ex]

Originally posted by nskukalek79
well i just hace 11:1 compression on a .040 over piston but i put two heli coils in and they just pulled out but then i found out that the guy torqing my studs was making them 45ft/lbs and they are just supposed to be 33ft/lbs, so i think he started stripping the threads before i rode at all

Ahh 33, 45 just a little difference:scary: :eek:


I don't think I would let that guy touch my motor ever again. :D

[soyo]

it is probably your studs, either striped out or stretched to much. i would go ahead and order heavy duty studs and be done with it.

and get the head inspected to see if it is warped