I tuned up my snowthrower (Toro PowerThrow 622 purchased 1999) today. When I shut off the engine after running it for a few minutes, a large amount of gasoline leaked out of the primer button and the carburetor. I restarted the engine without choking, then shut off, and a smaller amount leaked out. Should I worry? (FYI: During maintenance, I tipped the machine on its chute, as the instructions said that I could.) I'd appreciate some advice.