Valve Seals

Anyone know a simple way to tell me if my valve seals (seats ??) are going bad?

Is it BAck firing? Popping sounds through the exhaust when pressing or letting up on the Gas?
Do a leak down compression check, with air pump in the cylinder, of course if you had bad rings, it would leak down too, but with heavy oil, mebie it won't. The Haynes Manual describes how to do it...if you don't get a reply here...guess I'll stick to locks...at least they don't have seal problems....