I recently bought a 98 700 RMK took it out once and blew the head gasket. I took it to the local Polaris shop to get the engine fixed, haven't really been around sleds all that much so thought this would be the easiest way to fix and ride last winter. Took over a month to get the sled back. Once I got the sled and went to the mountains to ride. Seemed like it was idling a little low when I started the sled to warm up. After I let it warm up for a bit I hopped on and got on a trail. The sled had lots of torque and power when I started out, then a little ways down the trail it started to bog out and would barely move, like 5 mph. I picked up the back end of the sled and had a friend run the throttle. the track would start spinning and sounds like it regained all the power. Set the sled down, got on and took off with all the power again. It would backfire most of the time right before the power loss. Called the shop and they said it may just of had some bad fuel left over in the engine from when the head gasket got replaced, just told me to put more fresh gas in and run it. Same results with the fresh gas. I usually ride at about 10,500' So I don't know if it is a carb thing or what it is so I thought I would see if anyone on here could help me out with something to try. Thanks.