That's a BIG red flag warning about a sticking valve. If you started a sleeping engine without doing a lot of preliminary work, including using a clean gas tank, you've probably got more problems on the way. Varnish and gum from stale gas gets dissolved when fresh gas is added to an old tank, and it ends up in the valve guides. Broken rocker arms and bent valves from contact with the piston tops are other possibilities.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!