2007-2008 Polaris IQ Snowmobiles Service Manual, Page 86Get this manual
Fuel Systems The main system is designed to deliver fuel between low speed and high speed operationThis system is made up of the jet needle, needle jet, and main jetThe main system begins to take effect as soon as there is enough air flow into the carburetor venturi to draw fuel up through the main jet and needle jet assemblyThis system works in conjunction with the needle jet systemDuring low speed driving, there is very little clearance between the jet needle and the needle jet; therefore, very little fuel from the main jet can pass between the jet needle and the needle jetAs the throttle valve opening is increased, the tapered jet needle is raised farther out of the needle jet, allowing greater fuel flowUnder full throttle opening, the cross sectioned area of clearance between the jet needle and the needle jet becomes greater than the cross sectioned area of the main jetThus the main jet is now controlling the amount of fuel flowIn higher elevations and higher temperatures, the air is less denseVerify the production setting for your specific modelAll carburetors must be re-calibrated if operated outside the production temperature andor altitude rangeThe main jet installed in production is not correct for all altitudes andor temperaturesRefer to the jetting cart in the Specifications Chapter of this manual for correct jetting for altitude temperature rangesNOTE: It is the owner's responsibility to ensure that the correct jets are installed in the machine for geographical areaBe very careful when jetting down in warm weatherAs the weather turns colder it will be necessary to re-jet upward to prevent engine damageWhen selecting the proper main jet always use the lowest elevation and temperature that is likely to be encountered