Just as an engine needs extra fuel to start when it is cold, it is also possible to have too much fuel when it is warm. The stoichiometric ratio for petrol engines is 14.7:1. This means that to completely burn 1 kilogram of petrol you need 14.7 kilograms of air. This air-fuel ratio is critical to the engine running. If your compression is low you get less air, if you carburettor is blocked you get less fuel. Having too much fuel is just as bad though, and this is what is commonly referred to as having a flooded engine.

If the engine is already warm and you suspect it is flooded, make sure the choke is off and open the throttle wider. This will give the engine more air and less fuel. Be sure not to crank the engine too long if it won't start, it is easy to overheat a starter motor. Sometimes if an engine is flooded, waiting for the excess fuel to evaporate is the only way.