Cummins/Onan 305CCK / 5CCK — Tappet Adjustment
Adjustments · Valve tappets
For the Cummins/Onan 305CCK / 5CCK, from the Cummins/Onan operator's manual.
Applies to: Cummins/Onan 5CCK
Procedure
- Remove 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 align.
- Adjust each valve clearance so thinner gauge passes freely and thicker gauge does not.
- Turn adjusting screw as needed; screw is self-locking.
- For right cylinder, crank one complete revolution until marks align and repeat adjustment.
Tools required
- feeler gauges Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Intake valve tappet clearance 0.015 to 0.017 inch at 70°F.
- Exhaust valve tappet clearance 0.015 to 0.017 inch at 70°F.
Full service-parts list: Cummins/Onan 5CCK →
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.