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Hi Gang,
Our L-5 originally had a steel mesh air filter element made by the AirMaze company.
AirMaze Filters were on many WWII type planes and did a decent job if maintained well. They relied on fresh engine oil coated over the screen mesh to capture debris as it passed around the mesh.
The filter needed to be cleaned ( degreased) and reoiled at regular intervals . For many of us the filter was left unserviced during its life. This creates 2 problems. One ,the un oiled screen mesh will rust over time and break down the mesh allowing it to be ingested into the carb ( engine). Two, the filter is just blown out with air and not degreased. This captures large amounts of crud in the screen and blocks airflow.
I just cleaned an AirMaze off an AT-6 ,new to us, and found so much crud in the screen that light would no pass through it. ( AT-6 screens are thinner than L-5 screens, so you will not see light in our filters).
So , please clean and service the AirMaze air filters AT least every 25 hours. Soak filter in Mineral Spirits over night if you have any questions of the cleanliness of the filter. Blow the filter screen out FROM BOTH DIRECTIONS. then continue soaking another day and repeat the blow out. Once you get no debris and only clean air passing out of the filter then you are clean. That is the “heavy” clean.
A “normal ” clean servicing just needs to blow out with engine wash down gun ( both directions) and blow dry.
Once dry, you take an oil can with 50 weight engine oil (or 20W50) and and make several lines of oil across the face of the screen. ( like a tic ,tac, toe pattern). Let the filter sit, face up for about 2 hours. Then set it up on a an edge to drain excess oil out ( another 2 hours to overnight. Oil will migrate around the screen over time and cover all sections, so you do not need to dunk the whole filter in oil ( unless you want it to drain for weeks:). You can adjust how much oil you want to put on with practice.
When I do oil changes ,I remove and check the filter for condition and debris. I do this first. That way the filter is getting prepped while I am doing the other work.
The other air filter option is buying a new unit from Brackett Air Filters in Kingman, AZ . It is the BA-168 and used foam elements instead of a steel mesh. Scott Brackett ( owner) is very supportive of the older aircraft community and a really nice guy to boot. They have to custom make each BA-168 assy for us so don’t expect an overnight delivery for an” off the shelf “item. Last one I ordered was about 2 week delivery.
The Bracket filter is not automatically approved on L-5s so you will need to do a 337 or FAA filed approval for proper installation. I can help with this process. It is not scary,like it sounds:).
My only suggestion on the Brackett filter element is that when installing a new foam filter element, be sure and blot off and press out any extra liquid (it is thick like cold honey) or the filter will have a hard time breathing.
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