Cummins/Onan — Governor speed adjustment
Adjustments · Barber-Colman governor
From a Cummins/Onan operator's manual covering: 500 DFX-57R, 600 DFX-4R, 600 DFX-4XR, DFX 4R, DFX 4XR, DFX 57R, DFX 5DR, DFX 6DR, DFX 7XR, DFX 9XR. Check it applies to your exact model before use.
Applies to: Cummins/Onan 500 DFX-57R, Cummins/Onan 600 DFX-4R, Cummins/Onan 600 DFX-4XR, Cummins/Onan KT2300-G engine
Before you start
- Be prepared to assume manual control if adjustments are incorrect
Procedure
- Remove four screws and cover from governor controller
- Disconnect wire from TB11-22 to disconnect starter solenoid
- Place Run-Stop-Remote switch to RUN; governor should stay at minimum fuel position
- Return switch to STOP and reconnect wire at TB11-22
- Position speed control rheostat to midrange (out 5 turns from low rpm)
- Adjust speed reference potentiometer counterclockwise four complete turns
- Start engine; adjust speed reference potentiometer clockwise/counterclockwise to reach correct rpm
- Adjust gain potentiometer clockwise then counterclockwise until stable and responsive
- Load and unload engine several times to confirm gain adjustment
- Shut down and restart engine to confirm no overspeed
- Replace governor control box cover
Tools required
- screwdriver Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 1800 rpm for 60 Hz sets, 1500 rpm for 50 Hz sets
- frequency x 30 = engine speed
Full service-parts list: Cummins/Onan 500 DFX-57R →, Cummins/Onan 600 DFX-4R →, Cummins/Onan 600 DFX-4XR →
Source: Cummins/Onan operator's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.