Cummins/Onan — Valve Adjustment
Adjustments · Valves
From a Cummins/Onan owner's manual covering: 4B3.9, 4BT 3.9, 4BTA 3.9, 6B5.9, 6BT 5.9, 6BTA5.9, B5.9-160, B5.9-175, B5.9-190, B5.9-210, B5.9-230. Check it applies to your exact model before use.
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Before you start
- Disengage timing pin after locating TDC to prevent damage.
Procedure
- Remove valve cover.
- Locate TDC for cylinder No. 1 using engine barring gear and timing pin.
- Check/set valves with engine cold below 60°C [140°F]. Intake 0.254 mm [0.010 in]; exhaust 0.508 mm [0.020 in].
- Adjust valves per illustration. Tighten locknut and re-measure. Torque 24 N·m [18 ft-lb].
- Mark pulley and rotate crankshaft 360 degrees.
- Adjust remaining valves. Tighten locknut and re-measure.
- Install valve covers; tighten capscrews to 24 N·m [18 ft-lb].
Tools required
- 15 mm wrench Amazon
- 14 mm wrench Amazon
- flat blade screwdriver Amazon
- feeler gauge Amazon
- 3377371 engine barring gear Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Intake 0.254 mm [0.010 in] cold
- Exhaust 0.508 mm [0.020 in] cold
- Locknut 24 N·m [18 ft-lb]
- Valve cover 24 N·m [18 ft-lb]
Source: Cummins/Onan owner'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.