Ask the Editors: Causes of Flooding
Too much of a good thing.
Flooding is a very simple process in which excess gas in the top end soaks the spark plugs to the point where the plug can’t generate adequate voltage to form a spark; which, of course prevents ignition.
Contrary to common misconception, a carb itself can flood too. This happens when too much fuel enters the carburetor, trapping air in the bowl. Then adequate fuel can’t flow into the cylinder and the engine won’t start.
However, carb flooding wouldn’t be fixed by pulling and cleaning out the spark plug. This indicates that, as you guessed, either too much fuel is entering the top end at rest because of the broken fuel petcock. How so? It’s a device within the carb called the float that controls how much fuel is allowed into the float bowl. So if the petcock is not shutting off the gravity-fed fuel supply, the bowl (and float) will be up high at all times. The moment you try and start the machine, all of that fuel is allowed into the combustion chamber and you have a flooded engine.
If you’re not looking to replace the petcock right away, clamping the fuel line where it exits the tank may be an affordable solution.
You’ll know a lot more once you have access to the machine and can check to see if fuel is leaking out of the carburetor itself. A stuck float/needle inside the carburetor will cause flooding as the bowl is filling with gasoline due to gravity but the float is not shutting off the flow. This could happen because its sticking or gummed up. Either way a good carb cleaning can usually remedy the situation.
If all of this sounds like too much diagnostic work, do keep in mind eBay can set you up with a brand new carburetor for $15.
