How to Take a YFZ450 Carburetor Off and Clean It

Yamaha's YFZ450S is a high-performance all-terrain vehicle that relies on crisp throttle response to maintain an advantage on the race track. Dirt and debris can contaminate the YFZ450's fuel supply, which clogs the carburetor fuel jets that feed the engine. To maintain the YFZ450's competitive edge, you must remove and clean the carburetor as soon as you feel hesitation while riding. Using basic tools, most owners can can remove, disassemble and clean the carburetor in a single afternoon on YFZ450s produced between 2004 and 2007. Later models were fuel-injected.

Things You'll Need

• 4 mm Allen wrench
• 10 and 12 mm sockets
• Socket wrench
• Phillips screwdriver
• Pliers
• Plastic container
• Flathead screwdriver
• Carburetor cleaning solution
• Aerosol carburetor cleaner
• Air compressor with a blow gun attachment

Instructions

1. Release the seat latch, located at the rear of the seat, then pull the seat up and off of the ATV. Unscrew the gas cap, then remove the outer gas tank cover, using a 4 mm Allen wrench and a 10 mm socket. Remove the plastic side panels from both sides of the engine using a 10 mm socket.

2. Follow the throttle position sensor and carburetor switch wires, located on the left side of the carburetor, to their couplers on the ATV's wiring harness. Unplug the couplers. Remove the throttle cable cover, located on the right side of the carburetor, using a Phillips screwdriver. Pull the throttle cable end out of the throttle valve.

3. Set the gas tank fuel valve to the "Off" position using the valve selector lever. Pull the fuel hose off of the carburetor inlet, located on the left side of the carburetor, using pliers. Drain any fuel remaining in the hose into a plastic container.

4. Loosen the clamps attaching the carburetor to the engine intake flange and the air box flange using a flat screwdriver. Push the air box flange off of the carburetor inlet, then pull the carburetor to the side until it is free from the engine.

5. Hold the carburetor over your plastic container. Unscrew the drain bolt at the bottom of the float chamber, located under the carburetor, using a flathead screwdriver. Shake the carburetor gently until any fuel remaining in the float chamber is drained completely.

6. Remove the fuel hose and vent hoses from the carburetor using pliers. Remove the cap from the top of the carburetor, the carburetor switch assembly from the right side of the carburetor and the accelerator pump diaphragm and float chamber from the bottom of the carburetor using a Phillips screwdriver. Remove the choke diaphragm from the right side of the carburetor, located under the carburetor switch assembly using a Phillips screwdriver.

7. Pull the throttle slide and the jet needle out from the top of the carburetor. Remove the fuel jets from the jet towers, located under the carburetor, using a flat screwdriver. Remove the pin attaching the float to the float towers, near the jet towers, using a metal punch. Remove the float and needle valve by hand. Unscrew the valve seat using a 12 mm socket. Place the jets, jet needle, valve seat and float chamber in a carburetor cleaning solution.

8. Spray the carburetor body with an aerosol carburetor cleaner, especially through the carburetor's air and fuel passages. Clear loosened debris from the passages using an air compressor fitted with a blow gun. Air should travel easily though the carburetor.

9. Remove the jets and valve seat from the cleaning solution. Blow compressed air through the jets and valve seat to dislodge any remaining debris. Remove the jet needle and float chamber and blow dry with compressed air.

10. Reassemble the carburetor, then reinstall it into the engine intake flange. Push the air box flange over the carburetor inlet. Tighten the flange clamps, using a flat screwdriver. Hook the end of the throttle cable into the carburetor throttle valve, then reinstall the valve cover. Reconnect the fuel and vent hoses. Plug the carburetor switch and throttle position sensor connectors into the ATV's wiring harness.

11. Reinstall the fuel tank onto the ATV. Reconnect the fuel hose to the fuel tank valve and the carburetor fuel inlet. Unscrew the gas cap, then reinstall the fuel tank cover. Screw the gas cap into place. Reinstall the ATV's seat.

Tips & Warnings

• 2009 and newer YFZ450 models use an electronic fuel-injection system and do not rely on carburetors.

References

• Yamaha YFZ450S Service Manual; Yamaha Motor Corporation