Owners of 2003 and 2004 Yamaha RX Mountain sleds are encouraged to update their machines to the 2005 model specifications. Applying the 2005 model specs to the 2003 and 2004 models will minimize shift RPM loss at higher altitudes and provide better overall performance. Basically, the sled will run at the proper RPM more consistently, thus providing improved performance over the original 2003 and 2004 specifications. This suggestion comes straight from Yamaha as a way to enhance the high-altitude operation of these models. You can obtain these specifications from your local Yamaha dealer, or find them in any specification source for the 2005 model.