I was playing around on my bike today, and all was fine. Then out of no where it started running strangely. The motor was pinging (this was still the same tank of gas that I used when starting the bike and it ran fine). I drained this gas and got new gas, but the bike runs the same. Does being too rich make the bike pop or knock when the engine decelerates? It's pretty humid outside today and the bike seems to be loading up. I'm lost, as the bike has run fine all summer. I have a clean filter and all... Any ideas? I'm running 420 main, S-7 nozzle, stock needle in 2nd clip from top, and 2 turns out on air screw. Oh yeah, and a 25 pilot. (2001 CR250)