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Part-throttle range C
Operation with partly open throttle valve. This range is only influenced by the
jet needle (shape and position). The optimum part-throttle setting is controlled
by the idling setting in the lower range and by the main jet in the upper range.
If the engine runs on a four-stroke cycle or with reduced power when it is
accelerated with the throttle partly open, the jet needle must be lowered by
one notch. If then the engine pings, especially when accelerating under full
power at maximum engine revs, the jet needle should be raised.
If these faults should occur at the lower end of the part throttle range at a
four-stroke running, make the idling range leaner; if the engine pings, adjust
the idling range richer.
Full throttle range D
Operation with the throttle fully open (flat out). This range is influenced by
the main jet and the jet needle. If the porcelain of the new spark plug is found
to have a very bright or white coating or if the engine rings, after a short dis-
tance of riding flat out, a larger main jet is required. If the porcelain is dark
brown or black with soot the main jet must be replaced by a smaller one.
Draining the float chamber of the carburetor
Following every wet-cleaning procedure, the float chamber of the carburetor
should be drained in order to remove any water that may have penetrated into
it. Water in the float chamber leads to engine malfunction.
Make sure you do this while the engine is cold. Close the fuel tap, and place
a cloth under the carburetor, which is capable of absorbing the leaking fuel.
Unscrew the plug [1] and clean it with compressed air. Then, mount the plug
together with the gasket, open the fuel tap, and check the float
chamber for leaks.
FUEL IS EASILY FLAMMABLE AND TOXIC. WHEN HANDLING FUEL, BE SURE TO
EXERCISE THE UTMOST CAUTION. NEVER PERFORM ANY WORK ON THE FUEL SYS-
TEM NEAR OPEN FLAMES OR BURNING CIGARETTES. ALWAYS ALLOW THE ENGINE
TO COOL OFF FIRST. IMMEDIATELY CLEAN UP ANY FUEL WHICH MAY HAVE BEEN
SPILLED. MATERIALS SATURATED WITH FUEL ARE ALSO EASILY FLAMMABLE. IN
CASE YOU INGESTED FUEL OR FUEL SPLASHED INTO YOUR EYES, CONSULT A
DOCTOR IMMEDIATELY.
DISPOSE OF THE FUEL PROPERLY.
Checking the float level *
Arrange the carburetor diagonally at about 60° so that the spring in the float
needle valve is not pressed together. In this position, the edge of the float
should be parallel with the float chamber sealing surface (see illustration).
MAINTENANCE WORK ON CHASSIS AND ENGINE »
60°
JET NEEDLE
TYPE
RANGE OF ACTION
RICHER LEANER
NOZD
NOZE
NOZF
NOZG
NOZH
1
B
C
D
A
idle jet
throttle valve
air control screw
idle adjusting screw
main jet
jet needle
jet needle