My neighbor told me this morning that his sled will get up to about 65 or 70 and the engine just stops and the sled stops running. It's a 97 or 98 MXZ 583. I've never heard of anything like this with any sled, but maybe someone here has. The only thing I could think of is maybe something is wrong with the carbs, but I honestly don't really know. He said his dad's buddies told him it could have been the wrong size plugs. I didn't really think that sounded right, but I don't know. Any ideas?