0390106 JOHNSON HEAD ASSY,Commutator

Illustration 1 g01334425
Cylinder and valve location
(A) Exhaust valve
(B) Inlet valveIf the valve lash requires adjustment several times in a short time period, excessive wear exists in a different part of the engine. Find the problem and make necessary repairs to prevent more damage to the engine.Not enough valve lash can be the cause of rapid wear of the camshaft and valve lifters. Not enough valve lash can indicate that the seats for the valves are worn.Valves become worn due to the following causes:
Fuel injection nozzles that operate incorrectly
Excessive dirt and oil are present on the filters for the inlet air.
The load capacity of the engine is frequently exceeded.Too much valve lash can cause broken valve stems, springs, and spring retainers. This will produce emissions that are more than the correct specification.Too much valve lash can be an indication of the following problems:
Worn camshaft and valve lifters
Worn rocker arms
Bent pushrods
Broken socket on the upper end of a pushrod
Loose adjustment screw for the valve lashIf the camshaft and valve lifters show rapid wear, look for fuel in the lubrication oil or dirty lubrication oil as a possible cause.Valve Lash Check
An adjustment is not necessary if the measurement of the valve lash is in the acceptable range. Check the valve lash when the engine is stopped. The temperature of the engine does not change the valve lash setting.If the measurement is not within the acceptable clearance, adjustment is necessary. Refer to "Valve Lash Adjustment".Valve Lash Adjustment
It is important to follow this valve lash adjustment procedure. Do not use the traditional opposing cylinders method. Failure to follow the correct procedure may result in serious engine damage.
Note: The procedure to adjust the engine valve lash for the engine is different from conventional engines, due to the altered valve opening and closing events.
Table 2
Inlet Valves Exhaust Valves
Valve Lash 0.35 0.05 mm (0.0138 0.0020 inch) 0.35 0.05 mm (0.0138 0.0020 inch)
Firing Order 1-5-3-6-2-4(1)
(1) The No. 1 Cylinder is at the front of the engine.Note: For new engines, the valve lash should be checked and reset after the first 500 hours and after the next 500 hours. The valve lash will then be checked at service intervals of 1000 hours.Note: For example, if the pushrods in a remanufactured engine have been replaced with new parts then adjust the valve lash to 0.25 0.05 mm (0.0098 0.0020 inch) for the initial rebuild. The tappets should be reset to 0.35 0.05 mm (0.0138 0.0020 inch) at the normal service intervals thereafter.
Illustration 2 g01334426
Setting the valve lash
(A) Angled feeler gauge
(1) Adjustment screw
(2) Locking screw
Accidental engine starting can cause injury or death to personnel.To prevent accidental engine starting, turn the ignition switch to the OFF position and place a do not operate tag at the ignition switch location.
Illustration 3 g01334427
Typical example
Remove the valve mechanism cover. Refer to Disassembly and Assembly, "Valve Mechanism Cover - Remove" for the removal procedure.Note: When the valve mechanism cover is removed or installed, the electrical harness must be checked. Do not trap the injector harness when the valve mechanism cover is installed. Do not allow the harness to be in contact with the valve mechanism cover. Renew the harness, if the harness is damaged.
Table 3
Rotate the crankshaft until inlet valves are fully open. Set valve lash for the following :
Inlet valves
"(Cylinder number)" Exhaust valve
"(Cylinder number)"
11 9
(5) 10
(5)
3 5
(3) 6
(3)
7 11
(6) 12
(6)
1 3
(2) 4
(2)
9 7
(4) 8
(4)
5 1
(1) 2
(1)
See illustration 3. Rotate the crankshaft clockwise until the pair of inlet valves (11) is fully open. Measure the valve lash on inlet valves (9) and exhaust valves (10). If necessary, adjust the valve lash to the settings in Table 2. Complete the sequence of checks according to Table 3 until all the cylinders have been checked or adjusted.
Loosen the valve adjustment screw locknut that is on the adjustment screw (1).
Place Tooling (A