Yamaha YZ125X 2023 Owner's Manual

ENGINE8-3EAM30597JET NEEDLE ADJUSTMENTOn the carburetors used in the YZ125X the mainnozzle is a non disassembly type, so it can notbe replaced. Therefore, carburetor setting re-quires the change of the jet needle.1. The jet needle setting parts, having the sametaper angle, are available in different straightportion diameters and in different taper start-ing positions.* For AUS/NZL2. Effects of changing the jet needle (reference)• Diameter of straight portionChanging the diameter of the straight portionadjusts the air-fuel mixture when the throttleis 1/8 to 1/4 open.• Taper starting positionChanging the taper starting position produc-es the same effect as changing the clip posi-tion by 0.5 groove.Example:In case of being 0.5 groove leaner in relationto NYCF-2nd groove, choose NYDF-2ndgroove.EAM30598JET NEEDLE GROOVE POSITIONADJUSTMENTShould the engine be hard to run smoothly at in-termediate speeds, the jet needle “1” must beadjusted. If the mixture is too rich or too lean atintermediate speed operation, irregular engineoperation and poor acceleration will result.Whether or not the richness of the mixture isproper is hard to be determined by means of thespark plug and therefore, it should be judgedfrom your feeling of actual engine operation.1. Too rich at intermediate speedsRough engine operation is felt and the enginewill not pick up speed smoothly.In this case, step up the jet needle clip by onegroove and move down the needle to lean outthe mixture.2. Too lean at intermediate speedsThe engine breathes hard and will not pick upspeed quickly.In this case, step down the jet needle clip byone groove and move up the needle to enrichthe mixture.Standard jet needle NYCF*NYEEA. Difference in straight portion diameterB. Difference in taper starting positiona. Diameter of the straight portionb. Taper starting positionc. Richd. LeanNYCDNYCENYCFNYFFNYCFNYDFNYEFNYCGNYCHA. In case of being 0.5 groove leaner in relationto NYCF-2nd groove.a. Difference of 0.5 grooveStandard clip position No. 2 groove