Cummins/Onan — Governor Speed and Sensitivity Adjustment (Begin Spec R)
Adjustments
From a Cummins/Onan service manual covering: 10.0JC, 12.5JC, 15.0JC, 4.0JB, 5.0JB, 6.0JB, 6.1JB, 7.5JB, 7.6JB. Check it applies to your exact model before use.
Applies to: Cummins/Onan 10.0JC, Cummins/Onan 12.5JC, Cummins/Onan 15.0JC, Cummins/Onan 5.0JB, Cummins/Onan 6.0JB, Cummins/Onan JB engine, Cummins/Onan JC engine
Before you start
- An over-sensitive adjustment may result in a hunting condition.
Procedure
- Adjust engine speed by turning governor speed adjusting nut; clockwise increases speed, counterclockwise decreases.
- Adjust sensitivity by turning the sensitivity adjusting ratchet nut through hole in the blower housing.
- If speed drops too much at full load, turn ratchet nut counterclockwise to increase spring tension.
- After adjusting, replace dot button in blower housing and secure speed stud lock nut.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 60 cycle: 64 cps no load max, 57 cps min, 3 cps spread
Full service-parts list: Cummins/Onan 10.0JC →, Cummins/Onan 12.5JC →, Cummins/Onan 15.0JC →, Cummins/Onan 5.0JB →, Cummins/Onan 6.0JB →
Source: Cummins/Onan service 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.