Cummins/Onan 20W-20 — Adjusting Valve Clearance
Adjustments · Cylinder head / valves
For the Cummins/Onan 20W-20, from the Cummins/Onan service manual.
Applies to: Cummins/Onan 20W-20, Cummins/Onan RDJF engine
Before you start
- Four-cylinder engines do not have a BC mark on the flywheel.
Procedure
- Rotate flywheel clockwise until No.1 cylinder is on compression stroke at TC mark.
- Turn 10-45 degrees past TC.
- Check clearance between rocker arm and valve with feeler gauge.
- Adjust with lock nut securing rocker arm.
- Turn flywheel 180 degrees for No.2, then No.4, then No.3 cylinder, adjusting each.
Tools required
- Feeler gauge Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Valve clearance .017 in (.432 mm) cold
Full service-parts list: Cummins/Onan 20W-20 →
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.