All carburetors have fuel bowls. The fuel level in the bowl has a float, needle seat and spring that controls a fuel-inlet valve. The small spring or "tang" keeps the float in a certain position; it allows the fuel to enter and fill the bowl. When the float moves up, it shuts off the fuel supply to the bowl and deactivates the spring. Sometimes the spring can become bent or dislodged, requiring a replacement.
Set the shifter control in park for an automatic transmission. Place the shifter in neutral if the vehicle has a manual transmission. Use an end wrench to remove the negative battery cable. This procedure applies to tractors, riding mowers and other small engine applications, as well as automotive vehicles. Refer to your engine repair manual for the exact component parts that must be removed to gain access to the carburetor.
Remove the air-cleaner housing from the top of the carburetor with a screwdriver or socket. Small engines might have a hand-removable, screw-on filter in the top of the carburetor. Other designs employ a single-screw bolt or a stud-mounted butterfly nut; these require a slotted screwdriver or pair of pliers.
Locate the main fuel-inlet line that attaches to the top of the carburetor. Use a fuel-line wrench to remove the flared-cap nut on the line. Loosen the clamp with a screwdriver -- and pull the hose free -- if the main fuel-inlet line has a hose and clamp. Use a screwdriver to remove the screws on the carburetor top. Remember which length screws went into each hole.
Use a screwdriver to pry off the top of the carburetor; do not gouge the gasket between the two surfaces. Turn the carburetor-top upside down, and notice how the float drops at an angle. A small clip-spring -- called the "float-drop spring" -- allows the float to drop to a predetermined length on its hinges. It looks like a metal tang instead of a true spring. Gently pry the clip arms open, and pull out the spring.
Spread the spring-clip arms and engage them into their small mounts. Do not bend the spring. Use a float gauge -- and consult your repair manual -- to adjust the float drop. Let the float hang down. Measure the distance from the bottom of the float to the underside lip of the carburetor top. The measurement will be in thousandths of an inch. Adjust the float up or down by bending the tang portion of the float-drop spring.
Look at the spring on the pivot-hinge pin that allows the float to swivel up and down. If the spring does not extend to full length -- or has a deformity -- it must be replaced. Use a small tack hammer and a drift punch to knock the pin out of its guide holes. When enough pin shows from the end of the guide hole, use needle nose pliers to pull it out. The float will disconnect. Discard the old spring.
Realign the two float-swivel arms with the holes, and push the swivel pin into one hole. Set the new damper spring between the two holes; push the pin through the inside of the spring to the other mounting hole. Gently tap the the pin into its hole seats with the drift punch and hammer.
Place the carburetor top back on the carburetor. Insert the correct screws into their holes by hand. Tighten the screws with a screwdriver. Screw the fuel-inlet line back into the top of the carburetor. Tighten the flare nut with a fuel-line wrench. Replace the air-cleaner housing and tighten it down with a socket or screwdriver.
