ATV shuts off in gear

Hey guys, went to back my 08 Sportsman 500 up the other day and had some problems. Engine started fine. Put it in reverse and a second after I gave it some gas it shut off. The engine and screen. But immediately the screen would turn on. This kept happening and I noticed the it only did it if I gave it gas. If it was in neutral or park it would stay on, but in drive or reverse with gas it shut off. The weird part is if i give it just a tiny bit of breaking i could get it to go.

I plan on taking it in real soon to get it fully serviced and ready for ice fishing season, but dont want to pay up the pipe if its something simple. A guy at work thinks i have a bag pre-filter. It isnt stored at my house so I havent gotten a chance to get over and look at that yet.

Im not much of a mechanic so I’d appreciate any help I could get.

Thanks guys!