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Clean Snowmobiles: Operations
Table of Contents
Background and Overview
Reasons for Change
Preventing Pollution
Where To Go for Help
Complete List of Links

Essential Links:

How Two-Stroke Engines Work
Explains how two-stroke engines operate and their advantages and disadvantages.

Snowmobiles operate in cold weather. Like any internal combustion engine, these machines like to run rich in the cold, producing high amounts of carbon monoxide. Cold, stable atmospheric conditions combined with unfavorable topographical features like mountain valleys can "trap" snowmobile emissions, causing high atmospheric concentrations of pollution in areas with high snowmobile usage.

Traditional snowmobiles:

  • Utilize a two-stroke engine.
  • Are tuned to run "rich" (with excess fuel) for easier starting and reliable operation. (This results in incomplete combustion and the emission of high amounts of unburned hydrocarbons and carbon monoxide.)
  • Have recently been regulated but not required to use exhaust after treatment (such as catalysts) to reduce emissions.

Two stroke engines:

  • Feature a high power to weight ratio and good cold-start characteristics. However, they are inherently "dirty" engines.
  • Between 20 and 50 percent of the fuel, air, and oil mix can be emitted, unburned, from a two-stroke engine due to "short-circuiting" of the fuel-air mixture. (Short circuiting is when both the fuel injection and exhaust ports are open at the same time. There are no valves on a two-stroke engine.)
  • Partial combustion of traditional two-stroke oils results in visible particulate pollution

Most snowmobile tour operators replace their snowmobile rental fleet annually.

Technical papers from the Society of Automotive Engineers (SAE) have long been a source for keeping current with advancements in vehicle technology of all forms. SAE publishes about 2,000 papers each year which can be purchased online for a minimal fee. Some SAE publications related to the Clean Snowmobile Challenge are available free through a special grant arrangement with the Montana Department of Environmental Quality.


The Topic Hub™ is a product of the Pollution Prevention Resource Exchange (P2Rx)

The Clean Snowmobiles Topic Hub™ was developed by:

Peaks to Prairies Pollution Prevention Center
Peaks to Prairies Pollution Prevention Center
Contact email:

Hub Last Updated: 11/26/2012