You know, mechanical slide and constant velocity carburetors
used on motorcycles use a needle valve to control fuel flow through the
main jet. The tapered needle is fastened in the slider portion of the
upper carburetor and it slides down into the main fuel tube. And the
taper on the needle determines how much fuel can be drawn into the
intake stream. The needle position corresponds to throttle setting, all
the way into the tube for idle, and sliding most of the way out of the
tube for wide-open throttle. Carburetor needles may be adjusted to
lean out the main fuel circuit, or make it more rich. In general,
raising the needle in the slider will make the air and fuel mixture
more rich, while lowering the needle will lean it out.
To adjust carburetor needle valve, you should first get mechanic's tools and needle-nose pliers on hand. Only with good tools, can you do a perfect work.
Then, the first step is to remove the top of the carburetor. Turn the carburetor top mounting bolts counterclockwise until they are removed, then lift the top and slider from the carburetor body.
Next, remove the needle retainer from the slider. Push the needle up into and then out of the slider. Remove the locator clip on the needle with the pliers. And replace the locator clip in a lower slot to raise the needle and make the mixture more rich, or in a higher slot to lower the needle and lean the mixture out.
Then, re-install the needle in the slider and replace the retainer clip. Guide the needle and slider back into the carburetor body, ensuring that the needle slides easily into the main fuel tube. Re-install and tighten the carburetor top cap bolts to factory specifications for your make and model of bike.
Finally, test run the engine. Sneezing and popping back through the carburetor at high RPMs indicates a lean mixture and too low a setting on the needle. While excessive black smoke in the exhaust indicates a rich mixture and too high a needle setting. If these are the situations, you then need to repeat the steps to correct the needle position.
What is more, when adjusting needle valve, you have to always keep warning that the needle is a fairly delicate piece of metal, so you must take care to not bend or change the shape of the needle in any way. www.zjautoparts.net will show you more information.
To adjust carburetor needle valve, you should first get mechanic's tools and needle-nose pliers on hand. Only with good tools, can you do a perfect work.
Then, the first step is to remove the top of the carburetor. Turn the carburetor top mounting bolts counterclockwise until they are removed, then lift the top and slider from the carburetor body.
Next, remove the needle retainer from the slider. Push the needle up into and then out of the slider. Remove the locator clip on the needle with the pliers. And replace the locator clip in a lower slot to raise the needle and make the mixture more rich, or in a higher slot to lower the needle and lean the mixture out.
Then, re-install the needle in the slider and replace the retainer clip. Guide the needle and slider back into the carburetor body, ensuring that the needle slides easily into the main fuel tube. Re-install and tighten the carburetor top cap bolts to factory specifications for your make and model of bike.
Finally, test run the engine. Sneezing and popping back through the carburetor at high RPMs indicates a lean mixture and too low a setting on the needle. While excessive black smoke in the exhaust indicates a rich mixture and too high a needle setting. If these are the situations, you then need to repeat the steps to correct the needle position.
What is more, when adjusting needle valve, you have to always keep warning that the needle is a fairly delicate piece of metal, so you must take care to not bend or change the shape of the needle in any way. www.zjautoparts.net will show you more information.
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