Hi. I just bought my first atv a week ago. It's a 2003 250 recon. Starts and runs great but when I let off the throttle it kinda pops a little like i am running lean. I've backed off the richness screw but there's no differance. I took the spark ares. plug out of the muffler and made sure it was cleared. Any ideas? Is this normal? Might add that it's starts up on the first turn every time with no choke at all. Thanks for any help.