Artman, If I were you you I would have a oil analysis done to see how much dirt is in your oil, may also want to cut your filter open and take a look see. A regular air filter will take out material down to 20-30 microns where T-shirt would probably let in 100 micron size particles. A human hair is about 100 microns in diameter but there are only about 5 microns of clearance between your crank and bearings= big pieces of dirt wedging themselfs in side your motor. Shame on you, you should have a least used polyester.(just kidding) better get some real filter material on there before it is to late.