I have a 1998 hp500 I had to replace a head gasket. Now that I have done that I have no idea how to set the timming and valves. Please Help.

Probably need to call in a mechanic. When they are out of compression you use a filler to make sure the valves are tightened down correctly. I'm not sure what the correct measurement is on yours, and for timing you need a timing gun and a peice of white chalk.

The valve lash is easiest to set when the intake is off. You finger tighten the nut down until there is zero lash, then go 3/4 turn farther. The trick is to get the ones that only have spring pressure and not oil in them. If you have the intake off you can watch the plunger in the lifter and see when it starts to move, that is zero lash. After you get the 3/4 turn, tighten the retainer (allen wrench). Is this HP500 a carb or EFI so I can try and get your timing spec?

Have a pro do this for you. Risking and expensive engine is not wise. Lash and timing will cause severe damage if not done right.

Ditto