Last week my buddy who has had a lot of factory KX500's over the years, called. Chuck Sun had called him. He used to live down the street from my buddy. Said he just got a new 500 AF. Said it went through the gears too quick. Wanted to know what gearing to try. Nick told him go to a 15 up front to start with. Then start dropping the rear a tooth at a time till 1st is just about not usable. Nick runs 15/43 on his. My 500 is still stock gearing!!!!! Chuck told him he didn't think a steel framed KX500 would be too far behind the newer alum bike. Be interesting to see how he does racing the AF. Has to be a lot of fun to blow away any 450f in a class out there.