Yes a dirty air filter can cause it to flood even a slightly dirty one. All you can see is what is on the out side of the filter you can't see what is in the inside. Try washing it out and re-oiling it.
Any exhaust obstruction will also cause it to flood as well.
Another possibility is that the glow plug is going bad. It may not be bad enough to stop it from starting but it can cause it to run irradically.


rolland