My wife and I (I’m 74, she’ll be 73 next month) have just purchased 2 used ATV’s and riding them makes us feel like kids again. We are the proud owner’s of a 2004 yellow and a 2005 Mossy Oak (now purple) Sportsman 500 HO’s, both low mileage/hours. We went on a 29 mile trail ride Saturday and her’s ran Great. Mine did likewise most of the time. Pulling hills it would bog down like the choke was on. Had one very sharp rifle like backfire going down that same hill and it stumbled for a couple of minutes and then seemed to clear itself out and ran fine on the level ground. I pulled the plug (sure glad mine still had the tool kit with that special plug combo) after church yesterday and it is the correct NGK plug but it was really black and slightly damp. Cleaned it and checked the gap, which was correct. Re-installed fired it up and raced my wife around the pasture a few laps and it seemed to be ok. If this were the ’60’s and this was my ’56 ford 312 convertible I’d say the carb is jetted wrong (we live at 8500′ and were riding at approx 9500′. That carb looks likes it’s hard to get out. I’m not a mechanic. I’m still teaching high school- I guess that’s why this is so wordy. Any advice and/or tips?