The Softail M8 air cleaner on your Harley Davidson needs to be inspected and serviced at every major service. It’s also not a bad idea to simply inspect the M8 air filter when performing smaller services or oil changes.
For decades Harley Davidson has vented their motor crankcases directly into the air cleaner assembly. This is mainly to pacify the EPA. The venting air from the crankcase carries, along with it, an oil mist. The EPA prefers to have the vehicle burn the expelled oil as opposed to dripping it directly onto the ground.
The oil that doesn’t make it into the throttle body or intake manifold collects at the bottom of the M8 air filter. After awhile, if the filter isn’t cleaned, the oil will begin to drip out of the air cleaner assembly and down onto the areas below like your cam cover or exhaust pipes. Even worse, the oil will often blow back while riding, coating the right side of the bike or maybe even the rider’s pant leg.
It has been an increasingly more common concern amongst riders. Why am I having so much oil come out of my air box? Or, why do I have to clean my air filter so frequently? Well, the answer is simple; Harley’s motors have become incrementally bigger throughout the years. The bigger the engine, the more it breathes, or needs to vent. The solution is to simply be diligent about maintaining the air filter.
Harley suggests that the M8 air filter be cleaned with a mild detergent. Warm water and dish soap works very well. Use compressed air and blow out the filter from the inside out. Then, let it dry overnight. It is beneficial to purchase a second M8 air filter and have two in service. This way, you never have to wait for one to dry. You can alternate using the M8 air filters.
Remember, when focusing on this area of your motorcycle; service your way in, and service your way out. The filter is not the only component that will need to be cleaned. Wipe up the entire air box along with the opening of the throttle body. If the top breather bolts are weeping, take them out. Clean them and reinstall with teflon paste. Also, inspect the breather lines. Replace the lines if needed.
Service the M8 air filter on your Harley Davidson at every major service or as often as you find to be needed.