Craftsman 79193 Operation Manual - Page 9

iDLE SPEED ADJUSTMENT The idle speed of the engine is adjustable. An idle adjustment screw is between the air filter cover and the engine starter housing (Fig. 28). NOTE: Careless adjustments can seriously damage the unit. Aside from idle speed, only a Sears or other qualified service dealer should make carburetor adjustments. First, Check Fuel Old fuel is usually the reason for improper unit performance. Drain and refill the tank with fresh fuel prior to making any adjustments. Refer to Oil and Fuel Information. Second, Clean Air Filter The condition of the air filter is important to the operation of the unit. A dirty air filter will restrict air flow. This is often mistaken for an out of adjustment carburetor. Check the condition of the air filter before adjusting the idle speed screw. Refer to Air Filter Maintenance. Third, Adjust Idle Speed Screw _WARNING: The cutting attachment may spin during idle speed adjustments. Wear protective clothing and observe I all safety instructions to prevent serious personal injury, j If, after checking the fuel and cleaning the air filter, the engine still will not idle, adjust the idle speed screw as follows: Idle Adjustment Screw 1. Start the engine and let it run at a high idle for a minute to warm up. Refer to Starting/Stopping Instructions. Fig. 28 2. Release the throttle trigger and let the engine idle. If the engine stops, insert a small phillips in between the Air Filter Cover and the Engine Cover (Fig. 28). Turn the idle speed screw in, clockwise, 1/8 of a turn at a time (as needed) until the engine idles smoothly. NOTE: The cutting attachment should not rotate when the engine idles. 3. If the cutting attachment rotates when the engine idles, turn the idle speed screw counterclockwise 1/8 of a turn at a time (as needed), to reduce idle speed. Checking the fuel, cleaning the air filter, and adjusting the idle speed should solve most engine problems. If not and any of the following are true have the unit serviced by a Sears or other qualified service dealer: • the engine will not idle the engine hesitates or stalls on acceleration there is a loss of engine power ROCKER ARM CLEARANCE 5. Clean dirt from around the rocker arm cover. Remove the screw holding the rocker arm cover with a large flat blade screwdriver or Torx SC few RockerArm Cover ------_}B_ Spark T-25 bit (Fig. 30). Remove the rocker arm cover and Plug Hole gasket. 6. Pull the starter rope slowly to bring the piston Fig. 30 Adjusting Nuts to the top of its travel, (known as top dead iNTAKE center). Check that: • The piston is at the top of its travel. This should be done by looking into the spark Rocker Arms EXHAUST plug hole. (Fig. 30) Both rocker arms move Fig. 31 freely, and both valves are closed Exhaust Rocker Arm If these statements are not true, repeat step 6. Adjusting "-_---_J_ Nut _ / Feeler Gauge 7. Slide the feeler gauge between the rocker arm 0.003-0.006 in__ and the valve return spring. Measure the clearance between the (0.076-0.152 ram) Valve valve stem and rocker Fig. 32 arm (Fig. 32). Measure both the intake and exhaust valves. _ Stem The recommended clearance for both intake and exhaust is .003 - .006 in. (.076 - 0.152 mm). Use a standard automotive .005 in. (0.127 mm) feeler gauge. The feeler gauge should slide between the rocker arm and valve stem with a slight amount of resistance, without binding. See Figures 31 and 32. 8. If the clearance is not within specification: a. Turn the adjusting nut using a 5/16 inch (8 mm) wrench or nut driver (Fig. 32). To increase clearance, turn the adjusting nut counterclockwise. To decrease clearance, turn the adjusting nut clockwise. b. Recheck both clearances, and adjust as necessary. 9. Reinstall the rocker arm cover using a new gasket. Torque the screw to 20-30 in°lb (2.2-3.4 N,m). 10. Check the spark plug and reinstall. See Replacing the Spark Plug. 11. Replace the spark plug wire. 12. Reinstall the engine cover. Check alignment of the cover before tightening the screws. Tighten screws. WtrimAmRerNoIffNaGnd: aTloloawvoitidtosceoroiolubsefpoerresoyonual cinlejaunryo,arlwmaayisnttauirnnity.ourJI This requires disassembly of the engine. If you feel unsure or unqualified to perform this, take the unit to a Sears or other qualified service dealer. NOTE: inspect the valve to rocker arm clearance with a feeler gauge after the first 10 hours of operation and every 25 hours of operation. View of the Rear Engine Cover , The engine must be cold when checking or adjusting the valve clearance. This task should be Screws performed inside, in a clean, dust free area. Screws 1. Remove the six (6) screws on the back of the engine cover with a Flat-head or T-25 Torx screwdriver (Fig. 29). 2. Disconnect the spark plug wire. Fig. 29 3. Clean dirt from around the spark plug. Remove the spark plug from the cylinder head by turning a 5/8 in. socket counterclockwise. 4. Remove the engine cover (Fig. 29). 9