Section 3: Mechanical Governor; Governor Operation; Governor Internal Parts; Governor External Parts - Generac Power Systems GN190H Service And Repair Manual

SECTION 3: MECHANICAL GOVERNOR

GOVERNOR OPERATION

1. The governor SPRING tends to pull the LEVER and THROT-
TLE LINK toward the "INC. RPM" direction.
2. As engine speed increases, centripetal force acts on the FLY-
WEIGHT. When FLYWEIGHT centripetal force exceeds
SPRING force, the governor SPOOL is moved axially by FLY-
WEIGHT force. This causes the governor SHAFT to rotate,
which then moves the LEVER and THROTTLE LINK toward
a "DEC. RPM" direction.
3. As engine speed decreases, a point is reached where gov-
ernor SPRING force is greater than FLYWEIGHT centripetal
force. SPRING force then moves the LEVER and THROTTLE
LINK toward "INC. RPM."
4. Governor action consists of a series of small rpm overshoots
and undershoots, as SPRING force increases rpm and FLY-
WEIGHT centripetal force decreases rpm.
5. The point at which SPRING tension and FLYWEIGHT force
are equal is the governed speed of the engine.
GOVERNOR
GEAR
CENTRIPETAL
FORCE
FLYWEIGHT
CRANKSHAFT
(PTO END)
Figure 3.1 — Governor Operating Diagram

GOVERNOR INTERNAL PARTS

See Figure 3.2. A governor gear shaft is pressed into a bore
in the engine crankcase cover. Internal governor components
include (a) a THRUST WASHER, (b) GOVERNOR GEAR ASSEM-
BLY, (c) SNAP RING, (d) GOVERNOR SPOOL, and (e) GOVERNOR
SHAFT. A lockpin and washer retain the governor shaft in the
crankcase cover.
The governor gear assembly houses the governor flyweights.
Flyweight movement causes the spool to move axially. In
turn, axial movement of the spool results in rotation of the
governor shaft.
SPEED
ADJUST
SPRING
SHAFT
TO THROTTLE LINK
DEC. RPM
INC. RPM
SPOOL
CRANKSHAFT
GEAR
GOVERNOR
GEAR ASSEMBLY
THRUST WASHER
Figure 3.2— Internal Governor Parts

GOVERNOR EXTERNAL PARTS

Typical external governor parts are shown in Figure 3.3.
A GOVERNOR LEVER is clamped to the governor shaft.
Rotation of the governor shaft results in GOVERNOR LEVER
and GOVERNOR ARM movement. GOVERNOR ARM move-
ment moves the GOVERNOR ROD which, in turn, moves the
CARBURETOR THROTTLE ARM.
Tension of the governor SPRING can be adjusted by means
of the SPEED ADJUST NUT (Figure 3.3).
Figure 3.3 — External Governor Parts (Typical)

REMOVAL OF GOVERNOR EXTERNAL PARTS:

Before any covers and shrouds can be removed from the
engine, the governor external parts must be removed. Refer
to Figure 3.3 for the identification of the parts described in
the following procedure.
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GOVERNOR SPOOL
WASHER
SNAP RING
GOVERNOR
SHAFT
LOCK PIN