[2005GZ250]

Try this first, remove the gas tank & drain it & clean it. Drain the carb float bowl, there is a screw on the bottom right side of the float bowl just above a small hose that runs down the back side of the engine. Reinstall the tank and add a gallon of gas & 1/2 a bottle of "Seafoam", turn the fuel valve to "prime" and open the drain screw for a few seconds to flush any crud from the float bowl. Let the bike sit over night & then try to start it.