Try removing the carburetor bowl so you can clean it. I had this same problem last month and found a small piece of sediment that was keeping the float from dropping down. Good Luck

Harold, amckjk's advice is right-on. The engine has to have three things to run: fuel, air, and spark. You're evidently getting air (although you should clean or replace the air filter if you haven't). You're also getting both fuel and spark - at least some of the time. As a general rule, you either get spark or you don't - it either works or doesn't. Therefore, MOST LIKELY your problem is with fuel supply. As amckjk pointed out, sediment in the bowl can interrupt fuel flow. So can any number of other things. DON'T start out by "adjusting" the screws on the carburetor; as a general rule, they don't "un-adjust" themselves.

If cleaning the carb bowl doesn't fix the problem, try disconnecting the fuel line from the carb, and see if fuel gravity-feeds through the line. If it doesn't, then your fuel filter (if you have one) is stopped up, the line is kinked or blocked, or something in the tank is blocking the fuel.

If you haven't found the problem by now, I would suggest that the next step would be a thorough cleaning of the carburetor. Personally, I would probably install a rebuild kit at this time.

There are other things that could be wrong, but I suspect that if you've done the things listed above you'll be on the road again. Good luck.

Thanks, guys. I got it running. I took the sediment bowl off and found that the float was a bit sticky in its operation. I got it freed up and it started right up.