If it didn't have an air filter then dust, dirt and certainly grass clippings will be sucked into the engine and accelerate the wear on the engine. If you never put one on it would probably cut the life of the engine in half.
The air filter assembly is usually attached to it.
A lawn mower may leak gas from the air filter due to a carburetor issue, such as a stuck float or needle valve. This can cause excess fuel to flow into the air filter, leading to leakage. It is important to address this issue promptly to prevent potential safety hazards and damage to the lawn mower.
The air filter is usually located inside the canister that is bolted to the carburetor.
If you have fuel coming out of your air filter, then your carburetor bowl float is most likely gummed up an stuck. try tapping on the bowl, or you my need to take it off an clean it and the needle jet. How do you adjust air/fuel mix on a lawn mower motor?
under a plastic cover, next to the carb,
Most likely revving due to a dirty/clogged air filter.
make sure the gas valve is turned on and you put the air filter in right
Most use the B&S# 491588
Front of the engine screwed to the carburetor
Your lawn mower may be surging due to a dirty air filter, clogged fuel filter, or old spark plug. To fix it, try cleaning or replacing the air filter, fuel filter, and spark plug. You can also check the carburetor for any issues and adjust the throttle and choke settings.
Remove the air filter caseing disconenct the fuel pipe remove the bolts which hold the carb in place. L Davidson lawn mower tech
Most are shipped unoiled, and will need a few drops of oil. Check the instructions on the package.