My friend who is in the series for B class 250 and 125 c with his 2010 kxf told me that he has only had to spec his valves once with two years of heavy racing on the bike. He just says that he cleans his filter religously to keep the engine clean and thats all he does. He says the only engine maintence he does is upgrades. Feedback please. I have been cleaning my filter every 10 hours and was just wondering.