I have a 15 800 rmk I snow checked last year and I ride out of Albany. Had 10-60 weights in it last year and put 950 miles on it out there last year. I think I changed plugs after the first few tanks of fuel after it come out of break in mode cause I was told break in makes it run richer? I put 10-58 in it this year and it ran great with them when I was out over Christmas . Think I got a little more rpms with the lighter weights too. I am heading back out Tuesday and they are supposed to get dumped on will see how it runs this time. Where did you buy the sled from? That dealer should check it out for you without charging you since it was the first time you rode it. Some dealers aren't very nice if you didn't buy there which sucks.