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HS carburetor, tuning part 3

carb-17

Vehicles with emission control. Using the exhaust gas analyser, check that the percentage CO reading is within the limits given by the vehicle manufacturer. If the reading falls outside the limits given, reset the jet adjusting nut/ screw by the minimum amount necessary to bring the reading just within the limits given. If an adjustment exceeding three flats of the nut/half a turn of the adjusting screw is required to achieve this, then the carburetors must be removed and serviced

carb-18
carb-19
carb-21
carb-22
3615@2x

Step 1: With the fast-idle cam against its return stop, check that a 1.6 mm (1/16 in) free movement of the mixture control (choke) cable exists before the cable moves the cam.

Step 2: Pull out the mixture control (choke) (3) until the linkage is about to move the jet.

Step 3: Turn the fast-idle adjusting screw (4) clockwise until the correct fast-idle speed is obtained (see the vehicle manufacturer's recommendations).

Step 4: Refit the air cleaner.

Slacken both clamping bolts (1) on the throttle spindle interconnections.
Slacken both clamping bolts (2) on the cold start interconnections.

 

Using a balancing meter in accordance with the maker's instructions, balance the carburetors by altering the throttle adjusting screws until the correct idle speed and balance is achieved. Alternatively, use a 'listening tube' to compare the intensity of the intake hiss on all carburetors and turn the throttle adjusting screws until the hiss is the same.

Turn the jet adjusting nut/screw (3) on each carburetor down/clockwise to enrich or up/anti-clockwise to weaken, by the same amount until the fastest speed is indicated; turn each nut/screw up/anticlockwise until the engine speed just commences to fall.

Turn each screw very slowly down/clockwise by the minimum amount until the maximum speed is regained. From this setting adjust the mixture screws according to the vehicle manufacturer's recommendations.

Check the idle speed and readjust it as necessary with the throttle adjusting screws (4), turning each by the same amount.

Step 1: Vehicles with emission control. Using the exhaust gas analyser, check that the reading is within the limits given in the vehicle manufacturer's tuning data. If the reading falls outside the limits given, reset both the jet adjusting nuts/screws by the minimum amount necessary to bring the readings just within the limits. If an adjustment exceeding three flats/half a turn is required to achieve this, the carburetors must be removed and serviced.

Step 2: Set the throttle interconnection clamping levers (5), in accordance with the vehicle manufacturer's instructions, so that a clearance exists between the link pin and the lower edge of the fork. Tighten the clamp bolts, ensuring that there is approximately 0.8 mm (1/32 in) end-float on the interconnection rod.

Step 3: Run the engine at 1,500 r.p.m. and check the throttle linkage for correct connection by rechecking the carburetor balance.

Step 1: With the fast-idle cams of each carburetor against their respective stops, set the cold start interconnections, so that all cams begin to move simultaneously (6).
Step 2: With the fast-idle cams against their stops check that a 1.6 mm (1/16 in) free movement of the mixture control (choke) cable exists before the cable moves the cams.
Step 3: Pull out the mixture control (choke) until the linkage is about to move the jet.
Step 4: Using the balancing meter or listening tube to ensure equal adjustment, turn the fast idle adjusting screws (7) to give the correct fast-idle speed.

And finally refit the air cleaners.