Change the oil and filter, put some Sea Foam in the gas tank and the oil. Run it for a couple of hours then change the oil again. It sounds like the float is sticking in one of the carbs. If you can get to it with the handle end of a big screwdriver, sometimes you can tap on the bowl and get them to release. The Sea Foam will help clean out any trash and build-up. Make sure to run 93 octane gas only. You will get better performance from it over the 87 crap and eventually once everything is cleaned out your gas milage will go up. Hope this helps.
Treat every stressful situation like a dog. If you can't eat it or play with it, pee on it and walk away.