There are a bunch of half-donkey fixes that will be reccomended soon, but the only right way to do it is to take the head off, and have a good machine shop do a full valve job, including whatever is necessary to get the valve stem-to-guide clearance right. Sometimes that includes installing new guides and/or valves. The rocker arm and pushrod problems come from gummy deposits or varnish from stale gasoline that accumulates in the guides and locks up the valve stems. If you're still running the original gas tank, have it professionally cleaned, or replace it to prevent the crud from the tank from causing the same problems again.
Jerry
