I just bought a 1822 GrassHopper. It has a 18hp Briggs and Stratton on it. My problem is in the Carb.? When you start the mower you always have to choke it. When it starts when you push the choke in the motor will run wide open at at the lowest throttle point. If you pull the choke out the motor floods. And if you run with the choke half in the motor spits and sputters. Can these carbs. be rebuilt? Or do you have to buy a new one?$$$$$$ Also the mower will not start with the key. You have to turn the switch on and jusmp it across the silenoid and ideas? Thanks guys.