The air filter on a lawn mower is designed to catch impurities in the air (such as dust) and prevent them from entering the engine. Over time, the air filter can become clogged or dirty, and it will need to be cleaned or eventually replaced to keep the engine running well. Briggs & Stratton recommends replacing your air filter every year.
To replace the air filter on your Bolens 22" push mower, you'll need a flathead screwdriver, a new air filter (part #698369), and a small amount of engine oil.
1. Remove the air filter cover
The air filter is located on the top right side of the lawn mower if you're standing behind it. It sits under the air filter cover, which is held in place by one screw and is rectangular on three sides and almost pointed on the fourth side (the side facing the rear of the mower). Remove the screw in the air filter cover using a flathead screwdriver, then remove the cover by pulling it off.
2. Remove the old air filter
The air filter (the yellow foam piece) sits inside a plastic base. Remove the filter and base together, noting how the base fits onto the hole leading down into the carburetor. Then remove the air filter from the base. If you have a paper towel or rag handy, you can wipe down the base to clean it of dirt and dust.
3. Oil the new air filter
Add a small amount of engine oil to the new air filter by pouring it over the filter. Then squeeze and wring out the filter until all of the excess oil has been removed. If oil drips from the filter, wring it out some more until it doesn't drip any more.
4. Install the new filter
Sit the new air filter in the base in the correct orientation. You may have to force it to get it in place, but it's soft so it will bend easily. Then place the base back onto the hole leading into the carburetor, with the pointed end facing toward the rear of the mower (away from the spark plug). The base should sit firmly on top of the hole.
5. Reattach the cover
Place the air filter cover back on top of the air filter. It should line up perfectly with the base. Then put the screw into the hole in the cover and tighten it firmly.