I'm going to Colorado the first week in Sept. for some trail riding. Anyone here give me some info on how the 450 runs in High Altitude with standard jet? Also What is the purpose of the high speed spark plug that the owners manual talks about. Getting ready to change the plug, and was curious as to whether I should get one. I do alot of high speed trail riding ( for a foreman) Bike has 650 miles and 66 hours so I'm averageing 10 MPH. Thanks.