John Deere — Check and Adjust Valve Clearance (Four-Valve Head Engines)
Adjustments · Cylinder head / valve train
From a John Deere service manual covering: 4045, 4045TF120, 6068, 6068 HF485, 6068HF158, 6068TF120, 6068TF250, 6068TFM50, 6068TFM76. Check it applies to your exact model before use.
Applies to: John Deere 4045, John Deere 4045TF120, John Deere 6068, John Deere 6068 HF485, John Deere 6068TF120, John Deere 6068TF250, John Deere 6068TFM50, John Deere 6068TFM76
Before you start
- Adjust with engine COLD
- Replace valves, seats, springs and retainers in pairs; also replace bridge
Procedure
- Disconnect NEGATIVE battery terminal.
- Remove rocker arm cover and crankcase ventilator tube.
- Remove plugs from timing/rotation hole and timing pin hole.
- Rotate flywheel until No. 1 cylinder is at TDC compression; insert timing pin.
- Loosen jam nut on rocker arm adjusting screw.
- Turn adjusting screw until feeler gauge slips with slight drag.
- Tighten jam nut to 27 N•m (20 lb-ft) and recheck clearance.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Intake (rocker arm-to-bridge) 0.36 mm (0.014 in.) cold
- Exhaust (rocker arm-to-bridge) 0.46 mm (0.018 in.) cold
Full service-parts list: John Deere 4045 →, John Deere 6068 →, John Deere 6068 HF485 →, John Deere 6068TF250 →, John Deere 6068TFM50 →, John Deere 6068TFM76 →
Source: John Deere 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.