Troy-Bilt TB4BP Operation Manual - Page 12

Fig. 26 MAINTENANCE AND REPAIR INSTRUCTIONS ROCKER ARM CLEARANCE This requires disassembly of the engine. If you feel unsure or unqualified to perform this, take the unit to an authorized service center. NOTE: Inspect the valve to rocker arm clearance with a feeler gauge after every 25 hours of operation. • The engine must be cold when checking or adjusting the valve clearance. • This task should be performed inside, in a clean, dust free area. 1. Remove the eight (8) screws on the back of the engine cover with a Flat-head or T-25 Torx screwdriver (Fig. 30). Fig. 27 Air Filter Cover Remove Screws Remove Screws Air Filter Back Plate Tab Fig. 28 7. Reinstall the air filter cover. Position the slots on the top of the air filter cover onto the tabs at the top of the back plate (Figs. 24 & 28). 8. Swing the cover down until the tab on the air filter backplate snaps into place in the slot on the air filter cover (Fig. 28). CARBURETOR 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. 29). Idle Adjustment Screw NOTE: Careless adjustments can seriously damage your unit. An authorized service dealer should make carburetor adjustments. Check Fuel Old fuel is usually the reason for improper unit performance. Drain and refill the tank with fresh fuel Fig. 29 prior to making any adjustments. Refer to Oil and Fuel Information. 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. Adjust Idle Speed Screw If, after checking the fuel and cleaning the air filter, the engine still will not idle, adjust the idle speed screw as follows: 1. Start the engine and let it run at a high idle for a minute to warm up. Refer to Starting/Stopping Instructions. 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. 29). Turn the idle speed screw in, clockwise, 1/8 of a turn at a time (as needed) until the engine idles smoothly. Checking the fuel, cleaning the air filter, and adjusting the idle speed should solve most engine problems. If not and all of the following are true: • the engine will not idle • the engine hesitates or stalls on acceleration • there is a loss of engine power Have the carburetor adjusted by an authorized service dealer. 12 Fig. 30 2. Disconnect the spark plug wire. 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. 30). 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 T25 bit (Fig. 31). Remove the rocker arm cover and gasket. Rocker Arm Cover 6. Pull the starter rope slowly to bring the piston to the top of its travel, (known as top dead center). Check that: Spark Plug Hole • The piston is at the top of its travel while looking in the spark plug hole (Fig. 32). • Both rocker arms move freely, and both valves are closed. Fig. 31 If these statements are not true, repeat this step. Rocker Arms INTAKE Adjusting Nuts EXHAUST Feeler Gauge Spark Plug Hole Fig. 32