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Shimming the Needles

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Shimming the Needles

By Jim Sloot

If you've modified the stock air intake system, such as replacing the stock air filters with K&N units, or opened up the hole in the air box, you may experience a lean running condition, which manifests itself as hesitation and loss of power during heavy throttle application. This condition may be cured by slightly raising the carburetor needles by placing a shim washer under the C-clip which holds the needle assembly to the throttle slide. The steps for performing this simple procedure are outlined below:

Remove seat.
Turn off gas valve and remove gas tank.
Remove 2 screws from the diaphram cover.
Carefully remove the diaphram cover. Inside is a large spring which may pop out.
Pull the slide assembly out of the carburetor.

In the center of the diaphram is a white plastic plug held in with an O-ring. Pull this plug out to remove the needle assembly from the diaphram.

The diagram at right shows the OEM configuration of the needle assembly. Note the washer positions. At this point, you can move the top washer to the bottom, or leave it there and place an additional washer under the C-clip.

Replace the needle assembly into the slide and diaphram assembly. Be careful with the diaphram, it is fragile.

Replace the slide and diaphram into the carburetor.

Install the long spring and reattach the slide cover. Be careful not to pinch the diaphram and make sure it's properly seated in the groove.
Repeat for the other 3 carburetors.

Reassemble remaining parts and go for a ride.

Last update: 04:54 PM Sunday, September 26, 2004

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