Royal Enfield 350 BULLET 1989, Руководство по техническому обслуживанию мастерской

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WORKSHOP MANUAL BULLET
Page 71
TUNING THE CARBURETTER
With the correct specified main jet, throttle and needle setting, the engine can be tuned to a
nice tick-over by adjusting the pilot and throttle stop screws.
First take off the slackness in the throttle cable by means of the throttle adjuster screw
situated on the top ring and lock it by the lock nut. The throttle step screw can then be adjusted to
increase or decrease the idling speed of the engine by screwing it in or out respectively. With the
engine set at idling speed, to richen mixture, screw in the pilot adjuster screw and to weaken the
mixture unscrew it. The mixture should be set as weak as possible consistent with a steady
reliable idling speed and good acceleration If the engine is missing or lacks acceleration adjust
the throttle screw slightly and reset the pilot screw adjustment.
If the machine is used at very high altitudes or with a very restricted air cleaner a small main
jet will be necessary. The following table gives the reduction in main jet size required at different
altitudes:
Altitude ft.
Reduction
3,000
5%
6,000 9%
9,000 13%
12,000 17%
AIR CLEANER
The air supply to the carburetter is cleaned by a felt and gauze dry filter, housed in a box
bolted to the frame behind the carburetter.
Periodically once in every 3,000 Kms. the air filter element should be cleaned. It can be
removed from the air filter body by undoing the nut inside the body.
In case of paper element, if fitted, it should not be washed. The dust on the faces can be
blown off lightly with air and refitted.
During water wash and servicing of the vehicle care should be taken to see that the paper
element does not get soaked with water. Once in every 5,000 Kms. the paper element should be
renewed.
Causes of High Petrol Consumption
If the petrol consumption is excessive first look for leaks either from the carburetter, petrol
pipe, petrol tap or tank. If the system is free from leaks, carefully set the pilot adjusting screw as
described above. Running with pilot adjusting screw too far in is a common cause of excessive
petrol consumption.
If the consumption is still heavy, try the effect of lowering the taper needle in the throttle
slide (Do not fit a smaller main jet as this will not affect consumption except when driving on
nearly full throttle and may make mixture too weak at large throttle openings, thus causing over-
heating). Before doing so, however, make sure that the fault does not lie in the rest of the machine
such as (i) Brakes binding (ii) chains tight or dry (iii) engine requires decarbonising (iv) ignition
timing incorrect (v) spark plug defective.
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