MINSK Repair Manual page 26

Don't pump the petrol by pushing the petrol button on the side of the rectangle
carburettor. Then remove and open the carburettor and note where the level is with
respect to the two jets. Bend the brass connection point either a little up or down
to let more or less petrol in. Then connect the carburettor back to the engine, let it
fill again and check to see if you have got it right.
If the flexible brass connection point is adjusted so that the petrol level is too
low then the bike will run fine at speed but will stall when on idle. This is because
the idle jet is shorter than the accelerator jet, i.e. the accelerator jet will be
immersed but the idle jet will not. Conversely, if the float is set high then too
much petrol can get in and flood the spark.
(2) Adjusting the Idle Screw
The idle screw on top of the rectangular
carburettor or on the right side of the rounder one
regulates how much suction gets through the
system when the engine is at idle. Turning it
anticlockwise lifts the gate mechanism in the
carburettor in the same manner as turning the
accelerator. With the round carburettor you have
turn the screw clockwise for the same effect. In
both cases the engine's pitch will rise.
(3) Adjusting the Cable Screw
You can move the accelerator's wire casing up
or down by turning the screw at the top of the
carburettor where the wire goes in. This will then
raise or lower the gate, thereby controlling the
engine's speed at idle. This adjustment is made to
counter the effects of a stretched cable and to make
sure that the accelerator handle can be fully
twisted. Same for both carburettors.
(4) Adjusting the Air/Petrol Mix Ratio
A properly adjusted carburettor will produce a
sparkplug that is brown in the middle of its thread
and black around the bottom of the thread. Too
much air will make it white whereas too little air
will make it black.
On the rectangular carburettor the screw with a
spring under it on the left hand side controls the
amount of air mixed in with the petrol. On the
rounder version, this screw is very small and on the right-hand side.
©Digby Greenhalgh 2000
Minsk Repair Manual
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