20 Engine 10-2 Cylinder Head, Camshaft and Balancer Shafts Model 2120 Tractor TM-4252 (Dec-70) Remove plug from one end of rocker arm shaft and slide all parts off the shaft (see fig. 2). Identify parts for correct reinstallation. Injection Nozzle Bores Remove carbon deposits from bores, using special tool No. JDE 39. CAUTION: Always turn the tool clockwise as turning it counterclockwise will dull the tool. When several valves are being removed, identify each to facilitate replacement in its original posi¬ tion. Compress valve spring with commercial tool and re¬ move both retainer locks from the spring cap. Re¬ lease spring and remove spring cap and spring.
Pull valves out of the cylinder head. ASSEMBLY Rocker Arm Shaft Assembly Assemble the individual parts, according to fig. 3 finally placing the plug on the shaft end. Make Sure rocker arms are installed in their original positions. INSPECTION Check all parts for wear or damage. Valve Seats Measure diameter of valve guides. Replace valves, if necessary and ream the cylinder head bores. Be¬ side standard sized valves, there are valves with oversize stems available. Check if new valves move freely in the cylinder head. Reface valve seats in cylinder head with commer¬ cial tools, if necessary, observing specified measure¬ ments. Replace valve stem caps, if necessary.
Valve Springs Valve springs may have different free lengths, however, they must have the same length when compressed at the specified load. Check valve spring tension. L 50098 Fig. 3 - Rocker Arm Shaft Assembly and Valves —Exploded View Rocker Arm Shaft Assembly Make sure that all oil bores in the rocker arm shaft, rocker arms and the adjusting screws are clear. Thoroughly clean cavities of rocker arm supports. This is especially important for the rear support through which the oil passes to the rocker arm shaft. Check all rocker arms for excessive wear and tear on points of rocker arm contact. Check spring tension.
1 Plug 2 Rocker arm shaft 3 Special washers 4 Spring 5 Rocker arm 6 Adjusting screw 7 Rocker arm support 8 Cap screw 9 Valve stem cap 10 Keepers 11 Valve spring cap 12 Valve spring 13 Intake valve 14 Exhaust valve 15 Cam follower 16 Push rod If a valve is replaced, the accompanying rocker arm and push rod should be replaced at the same time. IMPORTANT: Make sure that oil bore in rocker arm shaft is at the side of the flywheel and facing down when assembly is installed on cylinder head. Lubricate all rocker arms liberally with oil and see that they move freely. Printed in Germany