Engine Tune Up
11. Position the remaining injector rack control levers as outlined in Steps 9 and 10.
Adjust Maximum No-Load Speed
With the engine running, move the speed control lever to the maximum speed position. Use an accurate
tachometer to determine the no-load speed of the engine.
NOTE: Do not over speed the engine.
Loosen the lock nut and adjust the maximum speed adjusting screw (Fig. 5) until the required no-load speed is
Hold the adjusting screw and tighten the lock nut.
Adjust Engine Idle Speed
Make sure the stop lever is in the run position and place the speed control lever in the idle position.
With the engine running at normal operating temperature, loosen the lock nut and turn the idle speed adjusting
screw (Fig. 6) until the engine idles at the recommended speed. The recommended idle speed is 500 rpm. However, the
idle speed may vary with special engine applications.
Hold the idle speed adjusting screw and tighten the lock nut.
Adjust Buffer Screw
With the engine running at idle speed, turn the buffer screw in (Fig. 7) so that it contacts the stop lever as lightly as
possible and still eliminates engine roll.
NOTE: Do not raise the engine idle speed more than 20 rpm with the buffer
screw. Check the maximum no-load speed to make sure it has not increased
over 25 rpm by the buffer screw setting.
Adjust Governor Booster Spring
The governor booster spring is used on some engines to reduce the force necessary to move the speed control lever
from the idle speed position to the maximum speed position. Adjust the booster spring as follows:
Move the speed control lever to the idle speed position.
Reduce the tension on the booster spring, if not
Fig. 6. Adjusting Idle speed
Fig. 5. Adjusting Maximum No-
Load Engine Speed