2007-2008 Polaris IQ Snowmobiles Service Manual, Page 87Get this manual
Fuel Systems Piston Valve Or Throttle Valve
The number following the letters on the jet needle is the serial number and it varies with individual jet needlesThe last number, 57 indicates that the outside diameter is 2.57mmThe smaller the O.D the richer the mixture
9DH01-57
intake side
The throttle valve controls the rate of engine air intake by moving up and down inside the main boreAt small throttle openings, air flow control is performed chiefly by the cutawayBy controlling air flow the negative pressure over the needle valve is regulated, in turn varying the fuel flowThe throttle valves are numbered 1.0, 1.5, 2.0, etc according to the size of the cutaway in millimetersThe higher the number, the leaner the gasolineair mixture
Jet Needle
The 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 needleThis needle (example) is 9DH01-57The first number is the approximate overall length in 10mm increments of the jet needleThe indicates the needle is approximately 90mm but less that 100mm in lengthThe letters on the jet needle indicate the angle of both tapersThe first letter designates the taper angle of the top section (closest to the grooves) and the second letter designates the angle of the bottom taperThe taper angles are graduated in 15' (15 minute) incrementsThe jet needle marked 9DH01-57 would have top taper of 1_0' and bottom taper of 2_0'