I've used the K&N filters as well as the H-D filters. They're good enough. After the first change having some debris on the sump drain magnet is expected. After that I would expect enough to possibly smear on the end of a finger. It's a good engine built to reasonably tight tolerances. Biggest problem is that it's air cooled and the oil takes a beating which is why synthetic is called for. The beast gets hot! Biggest thing is to change out the oil and filter religiously.
