4/18/2021 0 Comments Keihin Ktb Carburetor Guide
If this range is rich use a throttle valve with more valve CUT-AWAY (higher number).Carburetors are jetted using stock motorcycles and watercrafts.Measure the height from the bottom of the float to the Throttle Opening.When checking the float height, the float should be resting, but not depressing, the spring-loaded float valve pin.
This can be done by tilting the carburetor until the float tab just makes contact with the valve pin. If adjustment is needed, bend the metal tab on the float arm until correct height is obtained.--see example 1. Turn the IDLE MIXTURE SCREW or the AIR SCREW to for correct procedure, achieve highest speed and best response. The IDLE MIXTURE SCREW (FCR) controls fuel delivery to the idle port and the SCREW is located on the engine side of the carburetor slide. Turning the IDLE MIXTURE SCREW out will make idle and off-idle richer. Turning IDLE MIXTURE SCREW (CR, PWK, PJ, PE) controls the amount of air to the IDLE and SLOW CIRCUIT. This SCREW is located on the air cleaner side of the throttle slide and turning the SCREW out will lean the mixture and turning the SCREW in (clockwise) will richen the mixture. When you want a richer mixture in this range, use a larger SLOW JET or a smaller SLOW AIR JET. Changing the STRAIGHT DIAMETER (D) will change the calibration in the transition range from the SLOW circuit to the MAIN circuit (18 to 14) throttle. A smaller diameter will make this range richer and a larger diameter will lean this range. TAPER (A) changes are only made if there is a problem balancing the calibration between 14 and 34 throttle. If the mixture is rich at 14 throttle and lean at 34 throttle, a JET NEEDLE with a larger taper is needed. If mixture is lean at 14 throttle and rich at 34 throttle, change to smaller taper. If the calibration is lean from 14 to 34 throttle, raise the JET NEEDLE by lowering clip position, or use JET NEEDLE with shorter length (L1). If the calibration is rich, lower the JET NEEDLE with a longer (L1). Select the size of MAIN JET which offers the best W.O.T. MAIN JET for ideal engine durability. If a rich stumble occurs as the throttles are opened, the ACCELERATOR PUMP timing can be delayed by widening the gap on the ACCELERATOR PUMP linkage where it makes contact with the plastic lever. Reducing the gap will cause the ACCELERATOR PUMP to deliver fuel earlier. What the CUT-AWAY does is change the air velocity over the MAIN NEEDLE JET which changes when the MAIN SYSTEM begins delivering fuel. If the transition is lean change the throttle valve to a valve which has less CUT-AWAY (lower number).
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