How to Check the Carburetor Float Level on the 2001 Yamaha R6

The 599 cc engine used by Yamaha's 2001 YZF-R6 was fed via a quartet of Keihin CVRD37 carburetors. Like most motorcycle-specific carburetors, the CVRD37s used a float-based fuel supply, which used a floating valve that allowed more fuel into the carburetor's fuel, or float, chamber as fuel levels decreased. Under normal circumstances, the floats required little attention aside from periodic float level check. The check itself provides the current fuel level setting in each carburetor, which, if altered, could affect engine performance. A special fuel level gauge is necessary for this test, as well as a familiarity with the R6's fuel system.

Things You'll Need

• Motorcycle wheel chock or stand
• 4 and 5 mm Allen wrenches
• 10 mm socket
• Socket wrench
• Phillips screwdriver
• Fuel level gauge (Yamaha part no. 90890-01312)
• Gas can
• Shop towels
• Funnel
• Flat screwdriver
• Auxiliary fuel tank

Instructions

1. Place the motorcycle on a wheel chock or stand to hold it in a level, upright position.

2. Remove the rider's seat, using a 5 mm Allen wrench. Turn the fuel valve, located under the left side of the fuel tank to the "Off" position, then remove the fuel tank, using a 5 mm Allen wrench, 10 mm socket and a socket wrench. Pull the fuel hose off of the fuel valve outlet.

3. Remove the bolt from the tab on the front of the air box, located between the frame rails, using a 10 mm socket. Loosen the clamps attaching the bottom of the air box to the carburetor inlets, using a Phillips screwdriver. Pull the air box off of the carburetors. Remove the plastic rivets attaching the heat shield to the carburetors and the motorcycle's frame.

4. Install a fuel level gauge (Yamaha part no. 90890-01312) onto the first carburetor's float chamber drain tube, located on the bottom of the carburetor. Hold the gauge vertically in front of the carburetor, aligning the marks imprinted on the side of the carburetor with those on the gauge. Loosen the float chamber drain screw, using a 4 mm Allen wrench, to fill the gauge. Ideally, the fuel level indicated by the gauge will be between 0.69 to 0.73-inch (17.5 to 18.5 mm).

5. Tighten the float chamber drain screw, then pull the fuel level gauge off of the drain tube, using a shop towel. Empty the gauge into a gas can. Check the remaining carburetors' fuel level in the same manner.

6. Remove the float chambers from the carburetors, using a Phillips screwdriver, if the fuel levels are not within the specified fuel level ranges. Empty the float chambers into gas can, using a funnel. Push the metal pin attaching the float to the float towers, using a metal punch. Bend the metal tab at the center of the float upward with a small flat screwdriver to lower the fuel level, or downward to raise the fuel level. Reinstall the float and float chamber. Skip this step, if the fuel levels in all four carburetors are within specified fuel level range.

7. Refill the carburetor float chambers, using an auxiliary fuel tank connected to the carburetor fuel hose. Recheck the fuel level and make adjustments as needed.

8. Reinstall the heat shield onto the carburetors and the motorcycle's frame. Push the air box onto the carburetor inlets, then tighten the air box clamps. Screw the air box bolt into place. Reinstall the fuel tank and the rider's seat. Push the carburetor fuel hose onto the fuel valve.

Tips & Warnings

• Flammable vapors will be released while checking and adjusting the carburetor fuel levels. Do not work around an open flame or sparks to avoid igniting fuel vapors.

References

• Yamaha YZF-R6L Service Manual; Yamaha Motor Corporation