Why does the needle jet rub the throttle slide?
The needle jet is the last jet after the main jet for the gas to enter the engine. Every time you open the throttle, the needle which is attached to the throttle slide goes up and down and due to the air velocity of the air passing into the engine, there is slight pressure on one side of the needle which causes it to rub the needle jet.
How to tell if carb slides need to be replaced?
One simple test to see if the slides are contributing to the rough running is to hold the throttle at idle and then take up the slack on the cable by slowly turning the throttle – if the idle speed drops, it indicates that the slides are a loose fit in the carb body and should be replaced.
What does slide cut away mean on carburetor jetting?
The slide cut away generally effects the jetting in the ¼ throttle range at almost the same throttle position as the needle diameter effects. The slide cut away is usually predetermined by the engine manufacture or engine tuner. As a general rule do not change the slide cut away unless instructed to do so by a skilled engine tuner.
What causes carburetor to break up before full throttle?
Condition: Needle or needle jet is too rich. Carburetor runs clean to approximately ½ throttle but breaks up before ¾ throttle as a result of too rich condition. Correction: replace needle with next leaner diameter and test again.
How to adjust the CARB slide needle ( tuning )?
Dress up the ring of the throttle slide with a temp oily coat. It is going back to the carb, so you want to make sure the ring of the slide will sit firmly & create a good seal once fitted. This is to help prevent any unwarranted air leaks / external particle trapping.
The slide cut away generally effects the jetting in the ¼ throttle range at almost the same throttle position as the needle diameter effects. The slide cut away is usually predetermined by the engine manufacture or engine tuner. As a general rule do not change the slide cut away unless instructed to do so by a skilled engine tuner.
Condition: Needle or needle jet is too rich. Carburetor runs clean to approximately ½ throttle but breaks up before ¾ throttle as a result of too rich condition. Correction: replace needle with next leaner diameter and test again.
What causes a Keihin carburetor to sputter at low rpm?
A lean pilot jet setting will cause your engine to surge at very low RPM’s, bog or cut-out when the throttle is opened quickly and have trouble idling down. A rich pilot setting will result in hard starting, plug fouling at low RPM’s, sputtering as the throttle is cracked opened. The pilot jet isn’t difficult to set.