Carburetor Needle Adjustment Procedure

Work in Progress

Access the Carbs:

– Unlock the seat lock with the ignition key and remove.
– Remove the bolts on the left and right of the front side covers (3), disconnect the front turn signal, pull the tank vent hoses off of the fuel tank and remove the side covers.
– Open the tank cover, unscrew the fixing bolts (4) and remove the upper tank compartment.
– Remove the bolts on the lower tank compartment and the fuse box (5)(6), take the cover off the fuse box and dismount the lower tank compartment.
– Close the fuel cocks, disconnect the gasoline hoses, unscrew the
upper and lower fixing bolts on both fuel tanks (7) and remove the
tanks together with the lower vent hoses. Note: As an option, you may access the carbs by removing the right tank only. This is helpful if much “tuning” is to be attempted.
NOTE: it is easier to disconnect the gasoline hoses if you remove the
front bolts on the underride protection and fold the engine guard down.

Remove the Carbs:

– Un-screw the small screws holding the lid to the airbox. You don’t need to remove them.
– Unscrew the bolts (1) and remove the intake snorkel together with the frame from the air filter box.
– Disconnect the vent hose and the EPC hose and remove the upper half of the air filter box.
– Turn the intake trumpets (3) in a clockwise direction and remove.
– Remove the air filter.
– Unbolt both triangular side covers on the lower air filter box and remove the clamps on the carburetor connection boots.
– Detach the EPC hoses (4) from both carburetors and pull the hoses out of the lower air filter box.
– Remove both vent hoses from the carburetors.
– Lift both carburetors, carefully draw the cable for the idle speed
adjustment and the gasoline hose through the openings in the lower air filter box.
– Detach the fuel hoses from the carburetors.
– Tilt up the carburetors and fasten to the handlebar with a wire or rubber band. They do not need to be completely dismounted.
– Cover the intake manifolds with rags to keep foreign objects out.

Access the Needles

– Remove the diaphragm cover (5). Watch out that the slide spring doesn’t fly across the shop and land in the dust bunnies under the CNC machine.
– Remove the throttle slide spring and pull the throttle slide out of the carburetor together with the diaphragm.
– Press the jet needle holder together.
– Carefully unclip needle holder from the jet needle and remove.
NOTE: the spring on the jet needle usually remains in the jet needle holder. If it doesn’t, look under the CNC machine.
– Note the position of the tiny washers above and/or below the clip. You will need to replace them in the same location when done.

– The needle has 5 grooves in the top (blunt) end.
– The needle clip will be in the 2nd groove from the top, if it hasn’t been changed after the factory.
– Place the clip in the position you desire. Do the same for both needles.

– Check all parts for wear, especially the jet needle and the guide surfaces of the throttle slide.
– Check the throttle slide diaphragm carefully for cracks or fractures.
NOTE: the tab of the throttle slide diaphragm contains a small air jet. Be carefully not to lose it.

– Insert the spring in the jet needle holder and position in the throttle slide together with the jet needle.
– Clip the jet needle holder into place.
NOTE: a small air jet should be mounted in the tab of the throttle slide diaphragm.
– Insert the throttle slide and diaphragm in the carburetor, pushing
the jet needle in the needle jet.
– Mount the throttle slide spring and screw on the diaphragm cover.

-Now is a good time to check and/or adjust the idle mixture screws (#6 in photo to the right).


Put it all back together:

–– Replace the carbs on the intake manifolds in the reverse order of removal. Insert the front carb fully into the front rubber boot, and the rear should seat with very little force.  If your having trouble, a little rubber lube on the intake “rubbers” will allow the carbs to slide in much easier. RU-Glyde or silicone spray will help ease the process.  Both evaporate, or soak in quickly, so no residual lube is left behind.  If you find yourself “forcing” the carbs, check to make sure you have opened the clamps up fully, and neither of the rubbers have become folded over.  Make a careful visual check before “buttoning” everything back up.  Now’s the time to catch any mis-alignment. Tighten the boot clamps to 1.5 nm.
NOTE: Be very careful that the carbs are seated properly. Any air leak here will bolax up the engine running and cause you to pull your hair out!

– Replace the fuel tanks, glove box, and fairing pieces in reverse order of above. Be especially careful not to strip the large allen head bolts that hold the fuel tanks, as they are very soft.