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Tuning - Multi

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H Type Carburetter: Tuning (Multi-Carbs)

Remove the air cleaners and carry out the instructions in item 1 (single units) on all carburetters then:

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1

(a) Slacken one of the clamping bolts on the throttle spindle interconnections.
(b) Disconnect the jet control linkage by removing one or, in the case of triple carburetters, two of the linkage swivel pins.
(c) Carry out items 2 and 3 (single carburetters), then additionally:

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2

(a) Restart the engine and adjust the throttle adjusting screws on each carburetter to give the desired idling speed of 500 to 600 r.p.m. as recommended by the vehicle manufacturer.
(b) Compare the intensity of the intake "hiss" on all carburetters and alter the throttle adjusting screws until each "hiss" is the same.

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3

(a) Turn the jet adjusting nuts on all carburetters up to weaken or down to enrich the same amount until the fastest idling speed consistent with even running is obtained.
(b) Re-adjust the throttle adjusting screws to give correct idling if necessary.

4

(a) Check for correct mixture by gently pushing thelifting pin of the front carburetter up 0.8 mm (1/32 in). See Tuning Single Carbs for the possible effect on engine r.p.m.
(b) Repeat the operation on the rear carburetter and after adjustment re-check the front carburetter since the two are interdependent.
(c) Tuning Single Carbs item 5 shows the correct type of exhaust smoke.

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5

(a) Tighten the clamp bolt of the throttle spindle interconnections and set the link pin lever with the pin resting against the edge of the pick-up lever hole (see inset). This provides the correct delay in opening the front carburetter throttle disc.
(b) Re-connect thejet control linkage, so that both jets commence to move simultaneously.

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6

(a) Reconnect the mixture control wire with about 1.6 mm (1/16 in) free movement before it starts to pull on the jet levers.
(b) Pull the mixture control knob until the linkage is about to move the carburetter jets, and adjust the fast-idle screw to give an engine speed of about 1,000 to 1,200 r.p.m. when hot.
(c) Refit the air cleaners and re-check for correct mixture as described in item 4

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