Cummins/Onan 12.0 RDJC — Valve Clearance Adjustment
Adjustments · Valve train
For the Cummins/Onan 12.0 RDJC, from the Cummins/Onan operator's manual.
Applies to: Cummins/Onan RDJC
Procedure
- Check valve clearance with engine at room temperature, about 70 F (21 C).
- Turn flywheel until the cylinder to be adjusted is on its compression stroke.
- Turn flywheel clockwise an additional 10 to 45 degrees.
- Loosen locknut to increase clearance; tighten to reduce clearance.
- Check clearance between rocker arm and valve using a feeler gauge.
- Adjust in firing order (1-2-4-3) sequence.
- For #2, #4 and #3 cylinders, turn flywheel 180 degrees clockwise between each.
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)
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.