2004 Polaris Touring Service Manual, Page 119Get this manual
FUEL SYSTEM Mikuni TM Jet Needle Overview
Leaner Richer This needle (example) is 9DH0157The first number is the approximate overall length in 10mm increments of the jet needleThe indicated 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 9DH0157 would have top taper of 1_0' and bottom taper of 2_0'The number following the letters on the jet needle is the serial number and it varies with individual jet needlesO.DStraight Portion The last number, 57, indicates that the outside diameter is 2.57mmThe smaller the O.D the richer the mixture