Cummins/Onan — Adjust Valves
Adjustments
From a Cummins/Onan service manual covering: GNH-250, GNH-XI0, GNHC4, GNVH450, GV12, GV12 series, GV12-525. Check it applies to your exact model before use.
Applies to: Cummins/Onan GV12
Procedure
- Bar engine to No. 1 VS mark; both valves closed.
- Loosen locknut and back off adjusting screw.
- Insert feeler gauge between rocker lever and valve stem or crosshead.
- Turn screw down until lever just touches gauge.
- Tighten locknut to 70/80 foot-pounds.
- Final adjustment at engine operating temperature.
- Repeat for each cylinder per firing order.
Tools required
- feeler gauge Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- locknut torque 70/80 foot-pounds
- valve clearances in Table 3-2
Full service-parts list: Cummins/Onan GV12 →
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.