Cummins/Onan 4.0 BF-1R/9500 — Valve Tappet Adjustment
Adjustments · Valve system
For the Cummins/Onan 4.0 BF-1R/9500, from the Cummins/Onan service manual.
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Before you start
- Adjust valve clearance only when engine is at ambient temperature
Procedure
- Remove parts necessary to gain access to valve tappets
- Remove spark plugs to ease turning engine by hand
- Turn engine slowly using flywheel until left intake valve opens and closes; continue until TC mark aligns with gear cover TC mark
- Both valves should be closed; left piston at top of compression stroke
- Intake valve: .003 inch thickness gauge should just pass between valve stem and tappet
- Exhaust valve: .010 inch thickness gauge should just pass between valve stem and tappet
- Use 7/16 inch open end wrench to turn adjusting screw; hold tappet with 9/16 inch wrench
- Turn engine one complete revolution and align marks; repeat adjustment for right hand cylinder
- Replace all parts removed; tighten screws; torque manifold bolts
Tools required
- .003 inch thickness gauge Amazon
- .010 inch thickness gauge Amazon
- 7/16 inch open end wrench Amazon
- 9/16 inch open end wrench Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Intake .003 inch
- Exhaust .010 inch
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.