Air Filter Change on Briggs & Stratton L-Head Engine with Pulsa Jet Carburetor

Replace that dirty air filter, and keep an extra on hand for your Briggs & Stratton L-head engine with a Pulsa-Jet carburettor.

Foam air filter only 2-pack (part# 698369): https://amzn.to/3vXAPln Complete air box and filter (part# 5099K): https://amzn.to/3ppSfog

The holy trinity of combustion is spark, fuel, and air. All three of these factors play a necessary role in your engine starting and running efficiently. If any one of these three factors get out of whack, the snowball effect on the other two deteriorate the efficient operation of your small engine. 

The air filter on your lawn mower small engine is like the lungs of your body. When they get dirty and clogged up, it can be impossible for your engine to get enough air to run properly. It might run even clogged up, but your spark plug will foul with too much soot and oil deposits from incomplete combustion inside your engine. In the worst case extreme, your cylinder, valves, and piston will accumulate unburnt deposits of sticky and often crunchy fuel and oil. Chunks of that crud can and often break off and can break a piston ring, or score the inside of a cylinder so much that the engine can't run due to a lack of compression.

Often it's enough to just blow off the dust from a paper filter, but these types of engines utilize a foam air filter that usually needs to have a fine mist of engine oil to trap particles of dust and dirt. Foam filters too can eventually deteriorate and crumble into your carburettor intake. As long as the filter is not falling apart, you can clean the filter with warm water and any dish soap. These washed filters need to be completely dry, and re-oiled before replacement. You might find it easier to keep an extra one on hand in a sandwich baggy, already oiled up to replace quickly and keep on mowing. Clean the dirty one later, dry and oil it, and be ready for the next change. 

When removing the air-box to get to the filter, don't lose the air-box gasket that seals out dirt and dirt from entering your carburettor intake. Sometimes the gasket sticks to the underside of the air-box, and might fall off into the dirt or your garage floor never to be found again. The gasket is extremely thin and I've not found it to be purchased as separate item, only in complete kits: https://amzn.to/3ckIfr8

When re-assembling the air box, be mindful of placing the long screw that mounts the air box. It actually goes through the carburetor butterfly valve. If that valve get broken or jammed up, the entire carburetor can be replaced with the kit in the prior paragraph. 

Take note the air-box is five sided and the pointed end needs to point towards the back of the engine. The air-box can be crammed in backwards, but this places tension on the screw, possible obstructing the operation of the butterfly air valve. And the gasket will not seal the intake, and allow dust and dirt to bypass the air filer altogether and enter the engine.

I hope these tips and tricks can empower you with oracle like skills to make your small engines run smoothly and consistently.

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Wear your safety glasses, or you'll put your eye out. Try on some gloves. Take off that spark plug boot. Clean your room. Open the windows, those fumes are nasty. Just 'cause I do it, don't think it's the end all, be all solution. There's plenty more ideas out there, I can't take responsibility if you slice off a few fingers after watching my videos. And don't just pour that toxic stuff down the sewer or in the ditch, dispose of waste responsibly. Just be safe, OK?