Looking for some tech. advice on my snowmobiles guys! I have 2 Yamaha Mt Max 600,one was purchased in 97, the other in 98. The 98 sled burns a quarter tank more of gas than the other. No matter who rides it or what the trail conditions are--it always burns a quarter more than the other! I have had both sleds in fora complete service and they can't find the problem to the excess gas comsumption--everything meets specs!!!! Any suggestions?