Kohler Command CH20 Service Manual page 28

Fuel System
LPG/NG vapor enters regulator, then passes into primary
area, where pressure is reduced from up to 1724 kPa
(250 psi) at tank to 31 kPa (4.5 psi). Fuel pressure
against diaphragm overcomes spring and as movement
increases, spring will close lever. Primary diaphragm
breather is vented to secondary chamber so that rupture
of this diaphragm would direct fuel into carburetor.
Fuel now moves through passage, past secondary valve
into secondary area. As negative pressure (vacuum) is
created at carburetor venturi and is transmitted through
dry-gas hose to chamber secondary diaphragm is drawn
down and contacts secondary lever. Fuel will fl ow in
proportion to air velocity through carburetor venturi,
ensuring an ideal mixture at all engine speeds.
Whenever engine is operating, vacuum diaphragm is
down against fl oor and spring is compressed. Idle and
starting adjustment is made with a tamper-resistant
screw which regulates whisker wire system, opening
up secondary orifi ce slightly (but only when vacuum
diaphragm is drawn down). Very little vacuum is needed
to start this vacuum diaphragm travel: 0.2 in. Mercury
to start and 0.5 in. Mercury for full travel. When engine
stops rotating, loss of vacuum in section releases
diaphragm causing bumper to push against secondary
lever, overcoming action of whisker wire and ensuring
100% lock-off .
This patented Beam design will lock off primary
pressures up to fi ve times in excess of normal and
permits starting without priming or choking.
Nikki Regulator
Primary Chamber Details and Components
I
E
F
C
H
K
A Primary Valve
C Primary Chamber
Primary Diaphragm
E
Spring Adjustment
G Primary Valve Lever
I Primary Pressure
To Secondary
K
Chamber
28
G
A
D
B
J
B Primary Valve Seat
D Primary Diaphragm
F Contact Button
H Primary Lever Spring
J Fuel Inlet
KohlerEngines.com
Primary chamber reduces high pressure fuel fl ow from
tank and vaporizer down to approximately 29 kPa (4 psi).
Fuel fl owing from vaporizer enters inlet of regulator
under approximately 76 kPa (11 psi) of pressure. There
it is delivered to primary chamber through clearance
between primary valve and valve seat. As fuel continues
to fl ow and primary chamber approaches 29 kPa (4 psi),
primary diaphragm overcomes tension of diaphragm
spring. As diaphragm and contact button move up,
primary lever spring pushes primary lever up, in turn
closing primary valve and stopping fl ow of fuel. As fuel
is consumed and pressure in primary chamber drops
below 29 kPa (4 psi), diaphragm spring tension will be
greater than fuel pressure, causing primary diaphragm
to be pushed down. This causes contact button, to push
primary lever down, in turn opening primary valve and
admitting more fuel. In this manner, pressure within
primary chamber is maintained at a relatively constant
29 kPa (4 psi).
Secondary Chamber Details and Components
J
B
L
A
H
E
A Secondary Valve
C Secondary Chamber
Secondary
E
Diaphragm Spring
Vacuum Lock-off
G
Diaphragm
I Balance Spring
K To Intake Manifold
Secondary chamber further reduces fuel pressure from
29 kPa (4 psi) of primary chamber to near 0 kPa (0 psi)
pressure, to prevent excessive fuel fl ow to carburetor.
Fuel enters secondary chamber through clearance
between secondary valve and valve seat. While engine
is operating, and fuel is being drawn from secondary
chamber, secondary diaphragm is raised by atmospheric
pressure, simultaneously lifting secondary valve lever,
opening secondary valve, allowing fuel to fl ow. When
engine is running at idle, there may not be enough
vacuum created in carburetor venturi to overcome
tension of secondary diaphragm spring, and secondary
diaphragm cannot open valve. Under those conditions,
idle adjusting screw, and balance spring are used to
apply just enough pressure on diaphragm to maintain
suffi cient fuel fl ow for idle operation.
G
I
F D
B Secondary Valve Seat
Secondary
D
Diaphragm
Secondary Valve
F
Lever
H Idle Adjust Screw
From Primary
J
Chamber
L To Carburetor
24 690 30 Rev. G
K
C