Cummins/Onan — Adjusting Valve Lash
Adjustments · Engine valves
From a Cummins/Onan service manual covering: 5.5 HGJAA, 5.5 HGJAB, 5.5 HGJAC, 5.5 HGJAD, 5.5 HGJAE, 5.5 HGJAF, 6.5 HGJAA, 6.5 HGJAB, 6.5 HGJAC, 6.5 HGJAE, 6.5 HGJAF, 7.0 HGJAA…. Check it applies to your exact model before use.
Applies to: Cummins/Onan 5.5 HGJAD, Cummins/Onan 5.5 HGJAE, Cummins/Onan 6.5 HGJAE
Procedure
- Adjust when the engine is at room temperature.
- Remove the spark plugs so the engine is easier to turn over.
- Use a socket wrench on the generator pulley nut to turn the engine clockwise; remove the snap-in cover.
- Remove the valve covers with rags in place to catch oil.
- Turn engine until No. 2 intake valve is at max lift; adjust No. 1 intake valve lash.
- Turn engine until No. 2 exhaust valve is at max lift; adjust No. 1 exhaust valve lash.
- Turn engine until No. 1 intake valve is at max lift; adjust No. 2 intake valve lash.
- Turn engine until No. 1 exhaust valve is at max lift; adjust No. 2 exhaust valve lash.
- Secure valve covers using new gaskets and torque cover screws to 5.5 lb-ft (8 N-m).
- Replace the spark plugs and pulley nut cover.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Valve lash 0.004 inch (0.10 mm)
- Lock nuts 6.5 lb-ft (8.5 N-m)
- Valve cover screws 5.5 lb-ft (8 N-m)
Full service-parts list: Cummins/Onan 5.5 HGJAD →, Cummins/Onan 5.5 HGJAE →, Cummins/Onan 6.5 HGJAE →
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.