Intake Valve springs Failing? [Archive]

BraMas

03-20-2007, 10:19 PM

Whats up guys and gals joined the Forum about a month ago and just been trying to read everything about the 400EX. Anyway I have ? about mine before I parked my Quad for the winter it started making a knocking noise under load. So I got pissed parked it in the trailer and forgot about it until it now I want to go ridding. So I tare into the engine and find that both intake Valves are hitting the Piston. I talked to the local ATV shop and he said the springs on the 400ex are known to give out and cause problems. What would cause the Valves to be hitting the piston all of a sudden? Only thing I've done to the Quad is 11:1 piston and I have put a new crank in. But other than that I'm stock. Quad is a 02 400EX
Thanks for any info. Tim

underpowered

03-20-2007, 10:24 PM

sounds to me like your cam chain is stretched. when it stretches, it rolls the cam back and opens the intake valves sooner than it should possibly causing them to tap the piston. i would check your cam chain first off.