05 summit 800 ho running issue

Hey guys, got an issue on the wife's sled. It'll idle, but when you rev it to start moving its goes to 5 k or so then starts sputtering and stalling. Seems to run ok in reverse. It started as a bit of a misfire under load, then got worse and worse. Now every time you go to ride it, just about the time the clutch starts to engage, it stalls out. I was able to get it to the trailer in reverse, seemed to be running great. I'm at a loss. Anybody experienced something like this? Thanks, Brian

That was my concern, but usually it beeps if that's the issue. She's had it happen before, with a wiggle it'll usually fix it. This one doesn't beep at all. Also runs fine in reverse.