Hello...Im a newbie...2nd post. Couple quick ?'s...sorry if this has been way over talked about. Riding a 06 kx450f stock, bought new last year...40ish hrs, and started running bad (lean probs...throttle bog, popping on decel). Figured clogged jetting, dirty carb, so I pulled it a few days ago to clean, (also bought r&d adj fuel/air screw...figured it would be a good time to install). As Im pulling the ap cover and float bowl, i notice small rubber pieces, only to see that my ap diaphram looks like a small dog chewed on it??? This bike has been maintained, running premium pump gas,and has never sat for more then 3 weeks...How does this happen, and any suggestion for future?? Also, my first post was about ap o-ring mod, or just adjusting ap screw...got lots a great feedback, so i have merge adj leak pump on order right now. Was wondering how hard to tune in with air screw simultaneously, and possible recommended settings for sea level to 1800 ft. Any input would be much appritiated. Thanks agian.