Sputtering and back firing
Ok guys. I've been reading these forums for 2 hours. I'm down at hatfield McCoy in West Virginia. Riding my 2012 sportsman 800. Been fine all day. Blew the belt which I knew I needed to change. Put my replacement one on. And ride for another hour then the quad started to back fire and sputter when I would let off the gas and the check engine light came on. I did the turn the key thing it's a code 21. Which is loss of sync. Ok wtf does that mean. So I shut it off and waited for my buddies to come pick my quad up with the trailer. And when they got there I started it and the check engine light was off and it ran perfectly fine so sputter or back firing. The. We get back to the house and I decided to take it for a ride and a little into the ride the check engine light came on and started sputtering and back firing again. I called my hometown shop and they said they have no idea they would need to put the digital wrench to find out. Does anyone have any ideas to try and help salvage my expensive ass weekend down here. Thanks in advance for all the help.