The limiting speed mechanical governor is mounted at the rear of the engine, between the flywheel housing and the
blower (Fig. 1). The governor is driven by the right blower rotor drive gear. The left blower rotor drive gear is driven by a
shaft, that passes through the governor housing, from the engine gear train. There are two types of limiting speed
governor assemblies. The difference in the two governors is in the spring mechanism (Fig. 7). One has a long spring
mechanism, the other has a short spring mechanism.
After adjusting the exhaust valves and timing the fuel injectors, adjust the governor and position the injector rack control
NOTE: Before proceeding with the governor and injector rack adjustments, disconnect any supplementary governing
device. After the adjustments are completed, re-connect and adjust the supplementary governing device.
Adjust Governor Gap
With the engine stopped and at operating temperature, adjust the governor gap as follows:
Remove the high-speed spring retainer cover.
Back out the buffer screw (Fig. 9) until it extends approximately 5/8" from the lock nut.
CAUTION: Do not back the buffer screw out beyond the limits given, or the
control link lever may disengage the differential lever.
Start the engine and loosen the idle speed adjusting screw lock nut. Then adjust the idle screw (Fig. 8) to obtain
the desired engine idle speed. Hold the screw and tighten the lock nut to hold the adjustment.
NOTE: The recommended idle speed for non-EPA certified engines is 500-600
rpm, but may vary with special engine applications.
Stop the engine, clean and remove the governor cover and the valve rocker covers. Discard the gaskets. Start and
run the engine, between 800 and 1000 rpm, by manual operation of the differential lever.
CAUTION: Do not over speed the engine.
Check the gap between the low-speed spring cap, and the high-speed spring plunger with a .0015 " feeler gage. If
the gap setting is incorrect, reset the gap
Fig. 2. Adjusting Governor Gap
Fig. 1. Limiting Speed Governor
Engine Tune Up
adjusting screw (Fig. 2). If the setting is correct, the movement can be seen by placing a few drops of oil into the