Cummins/Onan — Valve Clearance (Lash) Adjustment
Adjustments · Valves/tappets
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan Performer P224 engine
Before you start
- Automatic startup of the genset while performing maintenance can cause severe personal injury or death. Push the control switch to Off and disconnect the negative (-) battery cable.
Procedure
- Remove the roof panel.
- Remove the intake manifold to access the valve tappets. Air cleaner housing may stay on carburetor.
- Remove the air intake screen from the engine divider panel.
- Remove the valve covers (use 7/16 inch socket).
- Remove the spark plugs (use 5/8 inch socket) to ease turning the engine.
- Rotate crankshaft clockwise with a 5/8 inch socket on the flywheel capscrew. When one cylinder's valve begins to move, adjust the opposite cylinder.
- Measure clearance with feeler gauge between valve stem and tappet.
- Use a 9/16 inch tappet wrench to hold the tappet; turn the 7/16 inch adjusting screw as needed. Screw is self-locking.
- For the left cylinder, turn engine one revolution until TC marks line up, then repeat.
- Replace all parts, use new gaskets, and torque all screws according to Thread Torques.
Tools required
- 7/16 inch socket Amazon
- 5/8 inch socket Amazon
- 9/16 inch tappet wrench Amazon
- 7/16 inch tappet wrench Amazon
- Feeler gauge Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Intake Valve Clearance (Cold) 0.005 inch (0.13 mm)
- Exhaust Valve Clearance (Cold) 0.013 inch (0.33 mm)
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.