Have 2004 KTM mxc 450. Person we bought the bike from said it was a mechanic special. It had a tick when we bought it. Got it home adjusted the valve. Tick still there. Took it for a ride for a few hours. Runs good but has a tick. Got it home and tore it down. Valves look good, but the intake have been touching the piston. Valves are straight, crank is tight, piston pin tight , no slope in the piston. On the parts breakdown only see one size for head gasket. Can someone help me with what I’m over looking. Thanks