2016 sportsman 850 issue. Need help.

2016 Sportsman 850 is getting real hot exhaust glowing red/orange. Seen a post saying to pull the spark plug and see what color it is to see if it’s running rich/lean/normal. Did that and spark plug looks fine. So could anyone tell me what else I could check/do to solve this issue? Polaris customer service is useless. Thanks.