I just bought a mulcher off Craigslist last weekend. 6 hp Briggs Intek 190. I ran 2 tanks of gas through it with no trouble. Stalled it a few times feeding wet leaves, but it started fine. Then I stalled it some time later, now it won't start. Pulled plug, have good spark. Put a little starting fluid in cylinder, but still wouldn't run, not even a sputter. Ideas?