Cummins/Onan Onan P4500i / P4500 — Checking/Adjusting the Valve Clearance
Adjustments · Valve train
For the Cummins/Onan Onan P4500i / P4500, from the Cummins/Onan operator's manual.
Applies to: Cummins/Onan Onan P4500i, Cummins/Onan P4500
Before you start
- Checking and adjusting valve clearance must be done when the engine is cold
Procedure
- Turn the generator off and allow the engine to cool for 30 minutes; work on a cold engine.
- Place the generator on a level surface in a well-ventilated area.
- Remove the engine service cover.
- Remove the rocker arm cover and carefully remove the gasket.
- Remove the spark plug so the engine can be rotated more easily.
- Pull the recoil handle to rotate the engine to top dead center (TDC).
- Verify both rocker arms are loose at TDC on the compression stroke; if not, rotate the engine 360 degrees.
- Insert a feeler gauge between the rocker arm and the valve stem to measure valve clearance.
- If adjustment is needed, hold the rocker arm pivot and loosen the pivot adjusting nut.
- Turn the rocker arm pivot to obtain the specified clearance; hold the pivot and re-tighten the nut to the specified torque.
- Recheck valve clearance and perform the procedure on the other valve if needed.
- Install the gasket, rocker arm cover, and spark plug.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Intake valve clearance: 0.0031 – 0.0047 in (0.08 – 0.12 mm)
- Exhaust valve clearance: 0.0051 – 0.0067 in (0.13 – 0.17 mm)
- Torque: 8-12 Nm
- Torque: 106 inch-pound (12 Nm)
Full service-parts list: Cummins/Onan Onan P4500i →, Cummins/Onan P4500 →
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.