Slow System (Low Degree Of Opening); Honda Motor Co.,Ltd - Honda Motorcycle Service Manual

FUEL SYSTEM
<Starting enrichment valve system (manual)>
As the starting enrichment valve is opened, the starting
enrichment circuit connects with the main bore. As a vacuum
is created in the main bore on starting, air and fuel (drawn
from the starting enrichment air jet and starting enrichment
fuel jet respectively) are injected into the main bore to supply
a rich mixture.
<Starting enrichment thermal valve system>
The starting enrichment thermal valve is a device for increasing
the volume of fuel. It is comprised of components such as a
PTC heating element, thermo-wax, a liquid medium, piston
and the starting enrichment valve.
The principle of operation is as follows:
When the engine is stopped and there is no production of
current from the alternator, the enrichment valve is
maintained in the raised position by a spring. In this position
the fuel increase circuit is fully open, ready for supply at any
time.
When the engine starts, fuel is supplied through the fuel
increase circuit.
At the same time, the alternator sends current to the PTC for
heating. The increase in heat is sensed by the thermowax
which begins to expand. The movement is transmitted
through the liquid medium to the piston, set collar and set
spring, and the enrichment valve is depressed. As the valve is
lowered, the jet needle starts to shut off the fuel increase
circuit, which, after a few minutes closes fully, ending fuel
comwensation.
Slow system (low degree of opening)
AS the throttle valve is only slightly open at low engine speeds
(degree of opening: fully closed - 1 /4), pressure on the intake
side is low, which allows some residual gas from combustion
to be sucked back into the intake manifold where
it
is mixed
with a fresh charge from the carburetor. The resulting mixture
is lean.
Low engine speed is linked with lower compression in the
cylinder, resulting in a richer mixture, and it is necessary to
raise the combustion velocity.
For this purpose, the engine includes a slow fuel supply
system which is separate from the main system.
ENRICHMENT
AIR FLOW
<.~;
STARTING
ENRICHMENT
AIR JET
ENRICHMENT
-rom PTC HEATER
iLTERNATOR
/
THROTTLE VALVE BY-PASS
SLOW JET
\
THROTTLE STOP SCREW
Date of Issue : March, 1995
o
HONDA MOTOR co.,LTD.
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