Kohler CH18-CH26 Service Manual page 70

Section 5A
LPG Fuel Systems
Impco (Beam) Regulator (See Figure 5A-20)
LPG vapor enters at point (A), then passes into
primary area (B) at point (28), where pressure is
reduced from up to 250 psi at the tank to 4.5 psi in
area (B). Fuel pressure against diaphragm (2)
overcomes spring (3) and as movement increases,
spring (5) will close lever (6). The primary diaphragm
breather (not shown in drawing) is vented to
secondary chamber so that rupture of this diaphragm
would direct fuel into the carburetor.
Fuel now moves through passage (E), past secondary
valve (25) into secondary area (C). As negative
pressure (vacuum) is created at the carburetor venturi
and is transmitted through the dry-gas hose to
chamber (C) secondary diaphragm (12) is drawn
down and contacts the secondary lever (16). Fuel will
flow in proportion to air velocity through the
carburetor venturi, ensuring an ideal mixture at all
engine speeds.
Whenever the engine is operating, the vacuum
diaphragm (10) is down against the floor (H) and the
spring (11) is compressed. The idle and starting
adjustment is made with a tamper-resistant screw (17)
which regulates the whisker wire system (not shown),
opening up the secondary orifice slightly (but only
when the 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. The instant the engine stops
rotating, loss of vacuum in section (D) releases
diaphragm (10) causing bumper (K) to push against
secondary lever (16), overcoming action of whisker
wire and ensuring 100% lock-off.
This patented Beam design will lock off primary
pressures up to five times in excess of normal and
permits starting without priming or choking.
5A.10
1
14
20
5
2
3
B
4
6
7
8
1. 1/8-27 NPT Plug
2. Primary Diaphragm Assembly
3. Primary Spring
4. Expansion Plug
5. Secondary Diaphragm Spring
6. Primary Lever Assembly
7. Fillister Head Screw
8. Primary Pivot Pin
9. Torx Head Screw
10. Vac Lock Diaphragm
Assembly
11. Vac Lock Spring
Figure 5A-20.
19
17
15
25
18
E
16
13
H
12
K
D
11
C
28 A
10
9 21
12. Secondary Diaphragm
13. Pan Head Screw
14. Secondary Lever Spring
15. Secondary Pivot Pin
16. Secondary Lever
Assembly
17. Adjustment Screw
18. Pan Head Screw
19. Expansion Plug
20. Diaphragm Gasket
21. Split Lock Washer