Help w/ 400EX Engine

[TRXMaddness]

First off I replaced all the valve seals and piston rings within my 400EX. After breaking it in it ate a exhaust valve and destroyed the head and piston.

Well, after replacing the head and boring the motor to a 402. I fired her up and there is still a clapping sound coming from the top end. Sounds like the same sound before it ate the valve. Could my piston rod or crankshaft bearings be shot and causing the clapping sound. It sounds like the valves are tapping on the piston, but there is no evidence.

[sampleez]

sounds like your timing could be way off, making the valves stay open too long and the piston hit them.

[cals400ex]

is your timing chain good? is the tensioner working properly? are the valves set to .005 intake and .006 exhaust to match the stage 2 cam?

[TRXMaddness]

sampleez.... Timing is good, double checked to make sure it was.


cals400ex... Timing chain is good, double checked it numerous times and the tensioner is good too. I thought the valves needed to be set at the stock setting, because it was still the stock valves and rocker arms. That has to be the problem then.

Thanks for your help... I will adjust the valves and hopefully that fixes the problem.

[cals400ex]

make sure you the bike is fully cold when you adjust the valves. yes, the stage 2 specs are .005 and .006.