I changed the oil on my '15 trike today. Also checked the air filter. The inside of my air cleaner cover housing is starting to rust at the bottom. Presumably where moisture would sit. I sprayed some silicone on it. You may want to check yours if you have this motor.

Be prepared of you are going to pull the air filter off. You will need a long shank T27 torx. You cannot get a tork socket in there unless the shaft is long. Just another HD, built for serviceability design.