Cummins/Onan 12.5 RDJC / 15.0 RDJC — Valve Clearance Adjustment
Adjustments · Valve train
For the Cummins/Onan 12.5 RDJC / 15.0 RDJC, from the Cummins/Onan operator's manual.
Applies to: Cummins/Onan 12.5 RDJC, Cummins/Onan 15.0 RDJC, Cummins/Onan RDJC
Before you start
- Incorrect valve clearance adjustment can lead to irrevocable damage to the generator set; only qualified personnel should perform this adjustment
Procedure
- Check the valve clearance when the engine is at room temperature, about 70°F (21°C).
- Turn the flywheel until the cylinder to be adjusted is on its compression stroke.
- Turn the flywheel an additional 10 to 45 degrees clockwise so the piston is in its power stroke with both valves closed.
- Check cylinder head-bolt torque prior to valve clearance adjustment.
- Loosen the locknut securing the rocker arm to the cylinder head to increase clearance; tighten it to reduce clearance.
- Using a feeler gauge, check the clearance between the rocker arm and the valve until the proper gap is established.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Intake 0.011 in. (0.28 mm)
- Exhaust 0.016 in. (0.41 mm)
- Cylinder head bolt torque 44 - 46 ft-lb (60 - 62 N·m)
Full service-parts list: Cummins/Onan RDJC →
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.