WM 80 Repair Carburetor Basics
wc_tx000522gb.fm 61
5.5 Bing Carburetor Operation
See Graphic: wc_gr002897
Fuel Feed:
The Bing carburetor does not use a fuel pump; instead, the fuel supply
is gravity fed. A priming button (a) is used during the initial start-up to
manually open the inlet needle valve (b) which primes the fuel chamber
(c).
Inlet Needle Valve:
While the engine is running, fuel flow into the fuel chamber is controlled
by the inlet needle valve. The inlet needle valve is operated by the
control diaphragm
(d). The control diaphragm is activated by the
vacuum created when air moves through the carburetor throat. A vent
to atmosphere provides the air pressure differential needed to create
the vacuum. This vacuum draws the control diaphragm towards the
carburetor throat and in turn opens the inlet needle valve allowing fuel
into the fuel chamber. Suction at the engine intake draws fuel out of the
fuel chamber, through the discharge ports into the carburetor throat.
As the fuel in the chamber is used up, atmospheric pressure pushes in
on the opposite side of the diaphragm pushing it towards the throat of
the carburetor. This diaphragm action lowers the inlet needle valve and
allows fuel to fill the fuel chamber. This fuel pushes the diaphragm
away from the carburetor throat and in turn closes the inlet needle
valve. In actual practice, the inlet needle valve assumes an averaging
position whereby the amount of the fuel entering exactly replaces the
amount being used.
b
c
d
e
a
f
g
h
wc_gr002897
To Next Page
Loading...
Need help?
General
