John Deere – 1023E, 1025R and 1026R – Adjust Valve Clearance

[1] – Park machine safely.

[2] – Be sure that ignition key is OFF before attempting to turn engine by hand.

[3] – Remove valve cover.

[4] –
?Top Dead Center (TDC)? is when the piston is at it?s highest point of travel in the cylinder on the compression stroke. Number one cylinder is closest cylinder to flywheel. There is a timing grid for each cylinder on the flywheel. Each top dead center mark has the cylinder number next to it.

From underside of machine, locate number one cylinder top dead center timing mark (A) on engine flywheel. Highlight mark with paint or similar light-colored mark.

[5] –
When top dead center is reached, the rocker arms for that cylinder will be motionless as the crankshaft is rotated. If rocker arms are still moving when TDC is approached, rotate crankshaft one full revolution and try again.

Turn the flywheel while watching for the number 1 cylinder TDC mark (A) to appear in the 1023E window (B) for 3TNM74 engines, the 1025R lower window for the 3TNV80 and 3TNV76 engines. Align the number 1 TDC mark (A) on the flywheel in the center of the window.

[6] – Try to move rocker arms push rods for No. 1 cylinder:
– If rocker arm and push rod are loose, the piston is at TDC on the compression stroke.
Proceed to next step.
– If rocker arms or push rods are not loose, rotate flywheel one revolution and align mark as in previous step again. Recheck rocker arm and push rods.

[7] –

Measure and adjust valve clearance only on the four valves indicated with arrows while number 1 piston is at TDC on compression stroke.

[8] –

Slide feeler gauge between valve cap and rocker arm to measure clearance (C). Valve clearance should be to specification. Adjust as necessary.

[9] –

Valve Clearance Adjustment

To adjust valves, loosen lock nut (D) and turn adjusting screw (E) until blade of feeler gauge can be inserted between rocker arm and valve cap. Turn adjustment screw to obtain a slight drag on feeler gage. Hold adjustment screw while tightening lock nut.

[10] – Recheck valve clearance after tightening lock nut.

[11] –

Normal Valve Cap – Not Normal Valve Cap

Check that valve cap on end of valve stem remained seated on valve and inside valve spring retainer.

[12] – Turn crankshaft pulley one revolution (360°) to the number 1 TDC mark again. This rotation puts the piston in number 1 cylinder at TDC on the exhaust stroke.

[13] –

Measure and adjust valve clearance on the last two valves (arrows) with number 1 piston at TDC of exhaust stroke.

[14] – Install rocker arm cover and tighten bolts to specification.