There are a few issues that can develop with a Generac generator. The first is if it won't start at all. When this happens you should look to the fuel tank first to determine if it is out of gas. This is an easy matter to resolve. If the fuel is OK, the other items can be looked at. First check the Generac engine on off switch to make sure it is in the on position. Also the spark plug should be tested to see if it has gone bad, and the wire connected to the spark plug slot should be checked to make sure it hasn't come undone.
If the engine is running rough, the Generac generator could have a fuel mix that isn't right or water in the fuel tank. If the fuel mix, is off a Generac service company will need to be called. If there is water in the tank. Drain the tank and carburetor and refuel. If it isn't any of these things, look to see if the intake valve is stuck. This will also require a repairman to fix.
Engine Works But No Power
If the engine is working fine but the Generac generator isn't putting out any power, then it could be the circuit breakers. Check and reset them to see if this is the problem. It could also be the connection itself of the item being powered. Both of these should be eliminated as the cause of power problems. If nothing else is found, then it is more than likely a fault in the generator and a repairman will need to be called.