159361-2020 ZEXEL 9 421 615 783 BOSCH GOVERNOR COVER 9421615783 1593612020 1157213400

INSTALLING ENGINE TURNING TOOLBoth the inlet and exhaust valves will be closed on compression stroke. First check the bridge adjustment and then the valve lash adjustment. Bridge Adjustment
Check the bridge adjustment screw and locknut for tightness. If the adjusting screw and locknut are tight, proceed with the valve lash adjustment. If the bridge adjusting screw can be turned with a screwdriver without holding the locknut, the bridge requires adjustment. The bridge adjustment must be made before the valve lash is checked for proper clearance.Make bridge adjustment as follows:1. Back off adjusting screw several turns (counterclockwise) making sure it is not in contact with the valve stem.2. Firmly press straight down on the rocker arm above point of contact with bridge.
ADJUSTING BRIDGE3. Turn the adjusting screw clockwise until contact is made with the valve stem, then turn the adjusting screw an additional 30° or 1/12 turn (1/2 the distance between the two points on the locknut).4. Hold the adjusting screw in this position and tighten the locknut to 20 lb. ft. (27.2 N m).
TIGHTENING ADJUSTING SCREW LOCKNUTValve Lash Adjustment
To prevent possible injury, do not use the starter motor to turn the flywheel.Hot engine components can cause burns. Allow additional time for the engine to cool before measuring valve clearance.
Measure the valve lash with the engine stopped. To obtain an accurate measurement, allow at least 20 minutes for the valves to cool to cylinder head and block temperature.
If the valve clearance is within 0.08 mm (.003 in) of the nominal clearance given, adjustment is not required. If the clearance is not within these limits, set the clearance as given in the chart. After checking the bridge adjustment, make the valve lash adjustment.1. With No. 1 piston at TDC on compression, check valve lash between the bridge and rocker arm. See chart for cylinder and valve adjusting sequence.2. To adjust, loosen valve adjusting locknut and turn adjusting screw to allow feeler gauge to pass between top of bridge and the valve rocker arm. Set the inlet valve lash at .015" (0.38 mm) and exhaust valve lash at .030" (0.76 mm). 3. After proper adjustment, tighten the adjusting screw locknut to 22 lb. ft. (29.9 N m) and recheck lash clearance. 4. Turn flywheel 360° in direction of engine rotation. Align flywheel timing bolt with the timing hole in the flywheel. 3408-No. 6 Cylinder will be at TDC on compression stroke (all valves closed)3412-No. 11 Cylinder will be at TDC on compression stroke (all valves closed).5. Check lash and adjust as necessary on all remaining valves, see valve adjusting sequence chart.6. Tighten locknut and recheck lash clearance.7. Remove engine turning tool and install timing access cover, timing bolt and plug.Check Valve Rotation: After checking valve lash and before the valve covers are installed, check the valves for rotation.1. Mark a line on each valve retainer.2. Start the engine and run at low idle.3. Watch the line mark on each valve retainer. Each valve retainer should turn slightly each time the valve