You can find the 8 HP Briggs and Stratton engine on a variety of service tools and mechanical systems, including water pumps, electrical generators, tractors and yard equipment. Briggs and Stratton 4-stroke engines use carburetor-metered gasoline to fire single cylinder engines. Most adjustments on the 8 HP model involve the fuel system and governor setup.
Unclasp the cowl case if your engine sits under the hood of a tractor or generator housing. Use a screwdriver to remove the air cleaner lid, or twist the knob handle by hand. Pull the air cleaner housing off the top of the carburetor and spray some carburetor cleaner down into the throat opening. Flip the throttle plate open with your finger, and allow the cleaner to seep down the venturi tube.
Pull the rope starter or activate the electric starter for your engine. Hold it at a fast idle until the engine warms up, then shut off the engine.
Refer to your owner's manual for the location of the idle-mixture screw. It sits in the side of the carburetor and has a slot screw adjuster head. Hook one clip lead of a small engine tachometer around the plug wire. Hook the other tachometer lead to ground. Use a slot-head screwdriver to turn the idle-mixture screw in clockwise until the needle lightly touches the seat, then turn the screwdriver counterclockwise 1 1/2 turns. Start the engine.
Look at the reading on the tachometer, expressed in revolutions per minute (RPM). Turn the idle mixture screw clockwise until the engine begins to stumble and you observe a drop in RPM. Slowly turn the screw in the opposite direction until you reach the highest RPM number on the tachometer gauge.
Make adjustments to the high-speed mixture screw, if you have an older Briggs and Stratton engine. Start the engine and raise the speed to the "high" or "fast" setting, then stop the engine. Turn the high-speed screw clockwise until the needle lightly touches the seat. Turn the screw counterclockwise 1 1/4 to 1 1/2 turns, and then stop. Start the engine and set the speed to "high" or "fast."
Turn the high-speed screw in clockwise until the engine just begins to slow down. Reverse the direction of the screw until the engine slows, then turn the screw back to the mid-point between the two stumbling positions. Observe the tachometer as you make increment adjustments for the highest RPM.
Keep the engine off. Locate the choke lever on the engine side case, or on the manual engine speed controls, and pull it out. Set the speed control to "high" or "fast" with the engine off. Locate the choke cable where it attaches to the carburetor linkage. Use a screwdriver to loosen the bracket screw that holds the cable in place near the linkage.
Push the cable forward or backward in the bracket until the choke valve closes inside the throat of the carburetor. Tighten the cable bracket screw with a screwdriver. Work the choke back and forth to test its full range.
Locate the governor arm linkage and spring that attaches to the throttle linkage. Consult your owner's manual. Make sure the governor linkage moves freely on the throttle linkage. To adjust the governor to factory specifications, loosen the nut on the governor arm with a small socket and push the governor arm down in a clockwise direction. Hold it there. Turn the governor shaft clockwise then tighten the nut with a socket.
