I have a 2001 honda trx400ex (factory effex) if that means anything, and im hearing an awful grinding noise when turn the motor over. I took off the valve cover checked the timing and the tensioner (Which is shot), and the spark plug. While i had it off i thought ill turn it over just for kicks, sure enough the sound was gone, it had next to no compression when i put my finger over the spark plug hole though. so i put the valve cover back on and adjusted the valves and turned it over and the noise was back. I had the rocker adjuster caps off and looked down in there and turned it over and the valves wouldnt complete a full cycle it looked like they were having a seizure. the Cam decompression mech was spinning and jumping around and if i put a screw driver down in it i could get it to stop and turn over it would turn over fine no noise, still no compression though, im at a loss any ideas and help would be greatly appreciated.