Trying to fix up a 12.5 HP RER for my nephew. It was running really rough, so I pulled the carb and cleaned it out. Wouldn't start. Pulled the plug and gas poured out. It has a fuel shut-off valve, which was turned on. Turned off the fuel shut-off, and turned it over a few times to get the excess fuel out of the cylinder. After that, it started up just fine. Ran it around, and it ran great. Got it to my nephew's house, and it started surging like it would starve for fuel, and then catch up. This carb doesn't have a fuel shut-off solenoid, but I saw a little tab with nothing attached. I'm wondering if that is what it's for. I told my nephew to make sure and close the fuel shut-off after each use. Anyway, any thoughts as to what could cause the surging and the gas in the cylinder? Thanks.