Cummins/Onan — Tappet (Valve) Adjustment
Adjustments · valves/tappets
From a Cummins/Onan service manual covering: 4CCK, 5CCK, 5CCK-150R, 5CCK-3CR. Check it applies to your exact model before use.
Applies to: Cummins/Onan 4CCK, Cummins/Onan 5CCK, Cummins/Onan CCK engine
Procedure
- Remove the valve covers.
- Crank engine slowly by hand until left hand intake valve opens and closes.
- Continue about 1/4-turn until flywheel mark and TC mark on gear cover are in line.
- Check clearance; thinner gage (minimum) should pass freely, thicker gage must not.
- Turn the self-locking adjusting screw to obtain correct clearance.
- Crank one complete revolution, line up marks, adjust right hand cylinder valves the same way.
Tools required
- Feeler gages Amazon
- Standard automotive-type wrench
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Tappet clearance 0.010 in. to 0.012 in., intake and exhaust
Full service-parts list: Cummins/Onan 4CCK →, Cummins/Onan 5CCK →
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.