When you take off the air filter, it pours out gas? Did you mean to say "As soon as I take off the fuel filter"?
Check the following, to make sure they are in good condition. Replace any items which aren't in good condition:
- Air filter.
- Fuel filter.
- Spark plug. (Check the gap on the spark plug.)
If all of these items are in good condition, it is possible that your fuel system is clogged with contaminants. In this case you need to drain the gas tank till it is empty, and get some new gas. Mix in some Seafoam gas treatment with the new gas, then fill up your tank with the new gas / Seafoam mix. If your engine will run for just a minute, the Seafoam will have the opportunity to clean out your fuel system. The engine will run like new afterwards, if that was the problem.
You can get Seafoam at most auto parts stores.