Cummins/Onan B43 / B48 — Governor Cup and Flyball Service
Repair & overhaul
For the Cummins/Onan B43 / B48, from the Cummins/Onan service manual.
Applies to: Cummins/Onan B48
Procedure
- With gear cover removed, remove the snap ring from the camshaft center pin.
- Catch the flyballs while sliding the cup off.
- Replace any flyball which is grooved or has a flat spot.
- Replace the ball spacer if its arms are worn or damaged.
- Replace the gear/spacer assembly if loose on gear hub.
- Replace the governor cup if the race surface is grooved or rough.
- If replacing the ball spacer, position it so an arm lines up with the space on the camshaft gear.
- When installing the governor cup, tilt engine so the gear is up, put flyballs in place, and install cup and snap ring on center pin.
- Check camshaft center pin extends 3/4 inch (19 mm) from end of camshaft, providing 7/32 inch (5.6 mm) in-and-out travel for governor cup.
Tools required
- snap ring pliers Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Governor cup travel 7/32 inch (5.6 mm)
- Camshaft center pin extends 3/4 inch (19 mm) from end of camshaft
Full service-parts list: Cummins/Onan B48 →
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.