Locknload82
01-01-2007, 03:15 PM
Ive got a 400ex, last spring had it overhauled, bored .20 over and 11:1 piston installed. ran great for 6 months then all of a sudden had a head bolt that pulled the threads in the cylinder. When I say head bolts I am referring to the studs that hold the head down to the cylinder, NOT the 6 mm valve cover bolts.
We took it apart and ordered heavy duty head studs from GT Thunder. 2 of the stock head bolts were tight in the threads, infact, so tight neither I nor the machine shop could get them out.
So we left the stock 2 bolts in, had the machine shop drill out the other 2 and retap them with roll form tap. when putting things back together they torqued down great. Quad ran great for about 5 hours after that, then one of the orginal stock bolts that we couldnt budge before pulled its threads.
Tore it back down, got the 2 original studs out and was going to put the heavy duty studs in them. Found out they had been helicoiled at some time. Can we still drill them out and roll form tap them and get them to hold?
Wonder if we have something else going on. My son has a 400ex bored out to 426 with 11:1 piston that is doing the exact same thing. we are using the stock all metal head gaskets. We are also using 93 octane gas and adding octaine booster.
Its odd that they are both doing the same thing at the same time. I had just started using the octaine booster last summer, about the time the problems started. Could that be causing the problems? Seems like the bolts torque down good, but then the threads pull after several hours riding (several heating and cooling cycles)
Any Ideas? I am tired of beating my head against a wall.....
We took it apart and ordered heavy duty head studs from GT Thunder. 2 of the stock head bolts were tight in the threads, infact, so tight neither I nor the machine shop could get them out.
So we left the stock 2 bolts in, had the machine shop drill out the other 2 and retap them with roll form tap. when putting things back together they torqued down great. Quad ran great for about 5 hours after that, then one of the orginal stock bolts that we couldnt budge before pulled its threads.
Tore it back down, got the 2 original studs out and was going to put the heavy duty studs in them. Found out they had been helicoiled at some time. Can we still drill them out and roll form tap them and get them to hold?
Wonder if we have something else going on. My son has a 400ex bored out to 426 with 11:1 piston that is doing the exact same thing. we are using the stock all metal head gaskets. We are also using 93 octane gas and adding octaine booster.
Its odd that they are both doing the same thing at the same time. I had just started using the octaine booster last summer, about the time the problems started. Could that be causing the problems? Seems like the bolts torque down good, but then the threads pull after several hours riding (several heating and cooling cycles)
Any Ideas? I am tired of beating my head against a wall.....