I have no idea why your carburetor leaks gas. For starters, I have no idea what type of engine you have. If it is a car, it is an old one since you do not have fuel injection. Maybe you should clean the grease and grime that has built up over the last 20 years off your carburetor and engine. Next, take a wrench, not a pair of pliers, and tighten the connections. They may have come loose. Now start your engine and try to see if you can tell where the gas might be leaking. Take the air filter off your carburetor.
If it was not a loose connection and is not a leaking tube that you can replace then you have done all you can do and need to take it to a regular mechanic.
Typically this is caused by a dirty carburetor causing gas to leak through and into the crankcase.
your float is stuck in the carburetor. Clean it with carb cleaner.
Dirty or stuck open needle valve in carburetor.
Seals, or float level.
The float valve in the carburetor is not working properly. You will need to remove the carburetor and clean it or replace it.
Stuck float?
Your carburetor is loading up. Or your needle valve is out of place or stuck.
1. drive it until you are out of fuel. it will quit leaking. 2. rebuild the carburetor. 3. replace the carburetor 4. identify the reason that it is leaking and then ask another question.
If it's coming out the overflow pipe, then it's likely to be a sticking float.
Three possibilities: The carburetor is set to run too rich, the plug is fouled and is not get sufficient spark, or there is a leak. Start with the leak and work backward: leak, spark, carb.
Most likely, Your float is stuck in the carburetor. If it is stuck open gas will continue to flow into the carburetor bowl, then it will flow into the crank case and cause your oil level to rise. You need to take off your carburetor and adjust the float.
More than likely this means your carburetor float has stuck at some point and let gas leak into the engine after it was shut off. To be safe you really need to replace the carburetor or have it cleaned.