Polaris 2001 High-Performance Snowmobile Service Manual (PN 9916690), Page 163Get this manual
CARBURETION AdjustmentsJet Needle and Float Level Fine Tuning the Mikuni Carburetor
A carburetor with piston type throttle valve is also called variable venturi type carburetorIn this type of carburetor, the needle jet and jet needle serve to control proper air fuel mixture ratio at the medium throttle valve opening (between 14 and 34 opening)Having the proper needle jet and jet needle has major impact on engine performance at partial loadThe jet needle tapers off at one end and the clearance between the jet needle and the needle jet increases as the throttle valve opening gets widerThe airfuel mixture ratio is controlled by the height of the "E" ring inserted into one of the five slots provided in the head of the jet needleThe chart at right shows the variation of fuel flow based on the height of the "E" ring2 4