Yamaha YZ250X 2023 Owner's Manual

ENGINE8-3EAM30596PILOT JET ADJUSTMENTThe richness of air-fuel mixture with the throttlefully closed to 1/2 open can be set by turning thepilot jet “1”. It is changed when adjustment can-not be made by the pilot air screw alone.A larger size jet results in a richer mixture at lowspeeds, and a smaller size in a leaner mixture.EAM30597JET NEEDLE ADJUSTMENTOn the carburetors used in the YZ250X, themain nozzle is press-fitted, so it can not be re-placed. Therefore, carburetor setting requiresthe 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.2. 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 NYHW-2nd groove, choose N3CW-1stgroove.Standard pilot jet #52Standard jet needle NYHWA. Difference in straight portion diameterB. Difference in taper starting positiona. Diameter of the straight portionb. Taper starting positionc. Richd. LeanNYHGNYHHNYHWN8RWN3EWN3CWNYHWNYHJNYHK