My Grandpas Polaris started fine and ran for a little bit (15min) but when he brought it back to the shed and tried backing it in the engine just ran with a deep hollow sound and would only go back a little. in order to engage the clutch that little bit it would have to rev up to an unusually high RPM. Then it would only work for a few feet when it would die. I tried changing it in to forward and it still lacked the power and sounded very hollow as it ran. Eventually, I just turned it off and pushed it into the shed. Any ideas as to what is going on? I don't want to jump blindly into a project if it is going to take more time or knowledge than I have.

 

If the engine run ok at an idle and higher throttle in neutral,I'd suspect worn down rear clutch ramp buttons along with a belt.If the buttons are ground down,the helix can grind metal to metal also. That would be my best guess as I've found plenty like this that would barely move or even not move at all. If the ramp button torque screws/sheared off in the clutch,sometimes hard to save the clutch assembly itself. On rare occasions a broken clutch spring can do the same thing. The circlip has to be removed from the rear of the clutch to allow the helix to pop up exposing the 3 buttons.Items 12,13,16 in the parts break down.Dirt Cheap Yamaha, Polaris, Suzuki & Kawasaki OEM Parts & Accessories – Cycle Parts Warehouse Plus here's a video on how the system is supposed to work. In a Sportsman 500,but operation is the same. Plus here's a good picture of ground down ramp buttons.