0386698 JOHNSON CARBURETOR REPAIR KIT

Valve Lash Check
A valve lash adjustment is NOT NECESSARY if the measurement of the valve lash is in the acceptable range. The acceptable range is given in Table 1. Caterpillar Inc. recommends adjustment of the valve lash after the following intervals:
The first 1000 hours of operation
2000 hours of operation
Every 2000 hours of operation
Table 1
Valve Lash Check    
Valves     Range for Acceptable Clearance    
Inlet    
0.52 to 0.68 mm (0.020 to 0.027 inch)    
Exhaust    
0.92 to 1.08 mm (0.036 to 0.042 inch)    Use the procedure that follows to check valve lash:
Rotate the No. 1 piston to the Top Center position. See Testing And Adjusting, "Fuel System". With the No. 1 piston at the Top Center position of the compression stroke, check the valves. See Testing and Adjusting, "Crankshaft Positions For Fuel Timing And Valve Lash Setting".
Adjust the valve bridges. See "Bridge Adjustment" for this procedure.
Insert the 6V-3075 Dial Indicator from the timing group into the 4C-6593 Adjustment Tool. Tighten the retaining screw finger tight.Note: Make sure that the 6V-3075 Dial Indicator is used with the short contact point.
Use the threaded hole that is nearest to the end of the rocker arm that will be adjusted in order to install the adjustment tool on the rocker base. Position the dial indicator stem over the flat area on the end of the rocker arm. Tighten the knob. Rotate the dial indicator so that the dial indicator can be easily read. Make sure that the adjustment tool is rigid and that the dial indicator stem moves freely.
Lift up firmly on the end of the rocker arm that has the adjusting screw and set the dial indicator to zero.
Lift up firmly on the valve end of the rocker arm and read the dial indicator.
Try to move the rocker arm while you are lifting up on the rocker arm. The dial indicator reading will vary. Read the dial indicator when the rocker arm is positioned in the groove of normal operation. Refer to Table 1 for the specifications regarding valve lash. If the dial indicator reading is within specifications move to the next valve.
If the dial indicator reading is not within specifications reset the valve lash. After the adjustment is complete proceed to the next valve. See "Valve Lash Adjustment".
After completing all of the valve lash checks and the valve lash adjustments for this crankshaft position, remove the timing pin from the crankshaft. Rotate the crankshaft to the next position. Install the timing pin in the crankshaft. Repeat Steps 2 through 8.
Remove the timing pin from the crankshaft when all valve lash adjustments have been completed.Bridge Adjustment
When the cylinder head is disassembled, keep the bridges and the respective valves together. To make an adjustment to the bridges, use the following procedure:Note: The bridges can be adjusted without removal of the rocker arms and shafts. Valves must be fully closed when the adjustment is made. See Testing and Adjusting, "Crankshaft Position For Fuel Timing And Valve Lash Setting" for information regarding the valve position.
Illustration 1 g00360773
Bridge Installation (1) Top contact surface (2) Locknut (3) Bridge
Illustration 2 g00360774
Bridge Adjustment (2) Locknut (3) Bridge (4) Adjustment screw (5) Bridge dowel
Lubricate the bridge dowel (5) in the cylinder head and the bore in the bridge (3) with 8T-2998 Lubricant .
Install the bridge (3) with the adjustment screw (4) toward the exhaust manifold.
Loosen the locknut (2) and the adjustment screw (4) for several turns.
Put a force of 40 to 60 N (9 to 13 lb) by hand straight down on the top contact surface (1) of the bridge (3) .
Turn the adjustment screw (4) clockwise, until the adjustment screw makes contact with the valve stem. Turn the adjustment screw clockwise for another 45 degrees in order to make the bridge (3) straight on the bridge dowel (5). Also, this additional rotation compensates for the clearance in the threads of the adjustment screw.
Hold the adjustment screw (4) in this position and tighten the locknut (2) to a torque of 100 15 N m (75 11 lb ft).
Put clean engine oil on the top contact surface (1) at the contact point between the rocker arm and the bridge (3) .Valve Lash Adjustment
The procedures for engine valve lash should be performed according to the information in the Service Manual.Operation of Caterpillar engines with improper valve adjustments will reduce engine efficiency. This reduced efficiency could result in excessive fuel usage and/or shortened engine component life.
Note: The first interval that is recommended for the valve lash setting for a new engine or a rebuilt engine is 1000 hours.
Table 2
Valve Lash Setting    
Valves     Dimension of Gauge    
Inlet    
0.60 mm (0.024 inch)    
Exhaust    
1.0 mm (0.040 inch)    Use the following procedure for the adjustment of the valves:
Rotate the No. 1 piston to the Top Center position. See Testing And Adjusting, "Fuel System". With the No. 1 piston at the Top Center position of the compression stroke, adjust the valves. See Testing and Adjusting, "Crankshaft Positions For Fuel Timing And Valve Lash Setting".
Adjust the valve bridges. See "Bridge Adjustment".
Insert the 6V-3075 Dial Indicator from the timing group into the 4C-6593 Adjustment Tool. Tighten the retaining screw finger tight.Note: Make sure that the 6V-3075 Dial Indicator is used with the short contact point.
Use the threaded hole that is nearest to the end of the rocker arm that will be adjusted in order to install the adjustment tool on the rocker base. Position the dial indicator stem over the flat area on the end of the rocker arm. Tighten the knob. Rotate the dial indicator so that the dial indicator can be easily read. Make sure that the adjustment tool is rigid and that the dial indicator stem moves freely.
Loosen the locknut on the rocker arm adjustment screw and turn the rocker arm adjustment screw clockwise until there is no valve lash. Loosen slightly. The valve lash should be at zero.
Set the dial in