Engine Tune-Up
CAUTION: Turning the band-level adjusting
Adjust Governor Speed Droop
nut does not in itself complete the adjustment.
The lock screw must be tightened to draw the
1. Remove the governor cover.
pivot arm assembly into the new position,
especially if the nut was turned down.
2. Set the governor speed droop bracket at its mid-
position (Fig. 7). After the other adjustments are
made, the speed droop may be increased if the engine
Adjust Idle Speed
speed is unstable.
There should be approximately 1/16" clearance
between the bottom of the idle speed adjusting screw
Preliminary Band-level Adjustment
head and the plunger directly under the screw head
(Fig. 8).
The band-level adjustment corresponds to the gap
adjustment on a mechanical limiting speed governor.
1. Close the governor operating solenoid valve switch,
In the low idle speed range, the governor pointer will
if a normally open type valve is used.
be between the 18 and 36 marks. As the speed is
increased, by moving the speed control lever, the
2. Start the engine.
pointer will gradually approach 18 and should be
exactly at 18 just below the full-load speed of the
CAUTION: Stop the engine if the speed starts to
engine. After full load is reached, the pointer will
increase above idle speed while the speed
move rather rapidly until at the no-load speed it will
control lever is in the idle position. Raise the
indicate a position approximately half way between
band-level again until the speed remains at
the 18 and 0 marks.
idle.
If the pointer is above 18 just below the full-load
3. If the engine stalls with the speed control lever in
speed of the engine, the band-level is too low; if the
the idle position, turn the idle screw down (clockwise)
pointer is below 18, the band-level is too high.
1/4 turn or until the engine will continue running.
P e r f o r m a preliminary band-level adjustment as
follows:
4. Hold the speed control lever in the idle position.
Then turn the idle speed adjusting screw (Figs. 8 and
1. Hold the linkage so the pointer indicates 18
10) in or out until the desired idle speed is obtained.
2. With a long thin screw driver, pry one of the
flyweights outward with a light force (Figs. 8 and 9).
It should reach a vertical position. If not, proceed with
Set
Band-level
at
18
Step 3.
1. Gradually move the speed control lever from the
idle to maximum speed position and while doing this,
NOTE: The position of the flyweights deter-
mines the position of the pilot valve plunger,
observe the movement of the pointer and also record
which controls the flow of oil to the servo
the top no load speed. The normal movement of the
piston If the flyweights are too far in, the
pointer in response to the speed control lever travel
should be as follows:
plunger will not close off the ports and oil will
flow to the servo piston. This will cause the
a. During the first 100 or 200 rpm increase above
terminal lever to move the pointer beyond
idle speed, t h e pointer s h o u l d m o v e f r o m
18 and result in excessive speed when the
engine is started. When the flyweights are too
approximately midway between 18 and 36 to
far out, the plunger moves up and dumps the
slightly above 18. Then, as the speed increases
oil from the servo piston. This causes the
on up to approximately 300 rpm below the top
no load speed, the pointer should move slightly
terminal lever to drop below the 18 position
until it is exactly at 18. From full-load speed up
and will result in difficulty in starting the
to no load speed, the pointer should move from
engine or in attaining speed.
18 to nearly midway between 18 and 0
3. Loosen the band level pivot arm lock screw and
b. If the pointer indicates more than 18 at
turn the band level adjusting nut (Figs. 8 and 10)
approximately 300 rpm below the top no -load
clockwise to raise the band level or counter clockwise
speed, the band- level is too low. The adjusting nut
to lower the band level Tighten the lock screw to
should be turned clockwise, in small increments,
draw the pivot arm assembly in place. Then check the
until the pointer indicates exactly 18 at the above
adjustment as described in Step 2. Readjust the band-
speed.
level, if necessary.
Page 136
