Polaris 2001 High-Performance Snowmobile Service Manual (PN 9916690), Page 139Get this manual
CARBURETION Main System (34 to Full Throttle)
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 flow
Throttle Valve Jet Needle By-pass Pilot Outlet