图片：http://www.snowridermag.com/2003/vintageracing
介绍：from wiki
A snowmobile (or skidoo or snow scooter, often referred to by enthusiasts as
a 'sled' and in the Canadian north and Alaska as a 'snowmachine') is a land
vehicle propelled by one rubber track with ski(s) for steering. They are
designed to be operated on snow and ice, and require no road or trail. Most
snowmobiles are typically powered by two-stroke gasoline/petrol internal
combustion engines. Four-stroke engines are becoming more and
