How to Clean the Carburetor on Bikes

by Contributing WriterUpdated June 12, 2017

If your Kawasaki bike motorcycle is having trouble starting or runs rough after a long period on inactivity, you may have a problem with the motorcycle's carburetors. Most likely, the small jets and passages within the carburetor have become clogged by debris or buildup, preventing fuel from reaching the motor. This can be caused by debris in the fuel tank, or more often, from the degradation of fuel over time, which creates a sticky "goo" that clogs the jets. The only effective method to remove these clogs is to disassemble the carburetor and clean it out.

Under The Hood:

 How to Clean the Carburetor on a CBR250RR

Turn off the ignition to the bike and set it on its side stand. If you've just been for a ride, allow at least 30 minutes for the engine to cool down.

Release the catch at the rear of the seat and remove it. This will reveal the anchor bolt at the rear of the gas tank. Remove the bolt and lift the gas tank. Disconnect the rubber hoses leading to the fuel petcock.

Remove the Phillips screws around the airbox. Lift off the cover and remove the air filter. This will reveal move Phillips screws that can be used to release the lower half of the airbox.

Lift out the airbox to reveal the tops of the carburetors. Undo the Allen bolts that hold them to the rest of the engine and lift them out of the frame.

Remove the fuel cock level by releasing the locking screw, then remove the four screws holding the diaphragm to the carburetor body.

Separate the diaphragm from the rest of the carburetor, then unscrew and remove the strainer cap, O-ring and screen. Spray all the parts with carburetor cleaner and wipe them off with a cloth. Rinse the jets through with cleaner. Reassemble and refit the parts.

Items you will need

  • Set of crescent wrenches

  • Phillips screwdriver

  • Set of Allen wrenches

  • Carburetor cleaner

 How to Clean a Carburetor on a Ninja 250

Lift the motorcycle onto its center stand and let the engine cool for at least one hour.

Remove the seat using the keyed release latch. Pull the side covers, located under the seat, off the motorcycle's frame. Remove the side fairing panels using a 5 mm Allen wrench.

Turn the fuel valve located under the left side of the fuel tank to the "on" position, using the valve lever or a flat-head screwdriver. Pull the fuel and vacuum hose off the side and rear of the fuel valve using pliers. Unscrew the fuel tank mounting bolts using a 10 mm socket and a socket wrench. Lift the fuel tank off the motorcycle, then unplug the fuel level gauge connectors from the bottom of the tank.

Disconnect the diodes and the headlight relay from the top of the battery cover, located between the seat rails. Remove the battery cover using a Phillips-head screwdriver. Disconnect the negative cable, followed by the positive cable, from the battery, using a Phillips-head screwdriver. Lift the battery out of the battery box. Remove the screws from the bottom and sides of the battery box, then lift the box out of the motorcycle's frame.

Unscrew the mounting bolts from the top of the air box using a 5 mm Allen wrench. Loosen the clamps attaching the air box ducts to the carburetor and the carburetors to the engine using a Phillips-head screwdriver. Push the air box ducts off the carburetor inlets, then pull the carburetors off the engine.

Loosen the choke cable holder screw, located at the top of the carburetor assembly, using a Phillips-head screwdriver. Pull the choke cable end fitting out of the choke arm. Loosen the throttle cable locknuts, located on the right side of the carburetor assembly, using a 10 mm open-end wrench. Turn the throttle cable adjusters clockwise to loosen the cables, then pull the cable ends out of the throttle valve. Unbolt the idle adjustment knob bracket from the left side of the motorcycle's frame using a 10 mm socket.

Loosen the float bowl drain screws, located on the bottom left side of both carburetors, using a flat-head screwdriver. Drain the remaining gasoline into a gas can, then tighten the drain screws. Remove the float chambers using a Phillips-head screwdriver, then place the chambers in a container filled with a carburetor cleaning solution.

Remove the floats and float pins from the bottom of the carburetors using a punch. Pull the needle valves out from the valve seats above the floats. Unscrew the float seat using a 12 mm socket. Unscrew the main jet from the needle jet holder at the center of the carburetors, using a flat-head screwdriver. Unscrew the needle jet holder using an 8 mm box-end wrench. Unscrew the pilot jet, located next to the needle jet holder, using a flat-head screwdriver. Place the main and pilot jets, as well as the needle jet holder, into the carburetor cleaning solution.

Remove the top caps from both carburetors using a Phillips-head screwdriver. Pull the diaphragm valve, valve spring and the jet needle out from the tops of the carburetors. Push the jet needles out of the diaphragm valves, then place them in the carburetor cleaning solution.

Remove the air cut valve from the left side of the carburetors using a Phillips-head screwdriver. Pull the air hoses off the top and bottom of the air cut valve.

Spray the fuel passages on the bottom of the carburetors as well as the air passages cut into the carburetor inlets with an aerosol carburetor cleaner. Clear any debris trapped in the passages using compressed air. Blow compressed air through the fuel hoses. Repeat until air easily can pass through all of the carburetor passages and fuel hoses.

Remove the jets, jet needle holder and needle valve seat from the carburetor cleaning solution. Blow compressed air through the holes at the center of the jets, needle holder and valve seat to remove obstructions. Hold the jets up to a bright light to ensure the jet passages are free of debris. Blow dry the float chambers and jet needles with compressed air.

Reinstall the needle valve seats and valve needles into both carburetors, followed by the floats and float pins. Screw the needle jet holders, main jets and pilot jets into place. Reinstall the float chambers.

Push the jet needles into the diaphragm valves, then slide the valves into the carburetors. Push the diaphragm springs down and reinstall the top caps onto both carburetors. Reinstall the air cut valve onto the left side of the carburetors, then push the air hoses onto the air cut valve.

Reinstall the throttle and choke cables, then push the carburetors into the engine's carburetor holders. Push the air box ducts over the carburetor inlets, then tighten the clamps on the front and rear of the carburetors. Screw the air box mounting bolts into place. Mount the idle adjustment knob bracket onto the motorcycle's frame.

Reinstall the battery box and battery onto the motorcycle. Connect the positive cable, followed by the negative cable, to the battery. Reinstall the battery cover, then reconnect the diodes and headlight relay.

Reinstall the fuel tank onto the motorcycle and reconnect the fuel and vacuum hose onto the fuel valve. Tighten the fuel tank mounting bolts to 7.6 foot-pounds using a torque wrench. Reinstall the side fairing panels and the seat onto the motorcycle.

Items you will need

  • Allen wrench, 5 mm

  • Flat-head screwdriver

  • Socket, 10 mm

  • Socket wrench

  • Pliers

  • Phillips-head screwdriver

  • Open-end wrench, 10 mm

  • Gas can

  • Container

  • Carburetor cleaning solution

  • Punch

  • Socket, 12 mm

  • Box-end wrench, 8 mm

  • Aerosol carburetor cleaner

  • Air compressor

  • Torque wrench

  • Gloves

  • Protective eyewear

 How to Clean the Carburetor on a Kawasaki

Turn the fuel valve off and remove the drain screw from the carburetor's float bowl with a screwdriver. Drain the remaining fuel in the float bowl into a container. Remove the carburetor from the motorcycle and place it on a clean, level work area.

Disassemble the carburetor. Use a screwdriver to remove the float bowl and top cover from the carburetor. Carefully remove the carburetor's gaskets. Pull the diaphragm and spring out of the top of the carburetor. Remove the brass slide in the throttle valve, using a screwdriver to remove its mounting bolts, and pull the slide out of the carburetor. Place these in individual marked plastic bags to prevent loss.

Remove the jets from the lower portion of the carburetor with a small flat screwdriver. Clean each jet as you remove them, spraying the jet with carburetor cleaner and clearing the jet's passages with compressed air. Place the jets in marked plastic bags.

Clear the passages in the carburetor with carburetor cleaner and compressed air. Spray the float bowl liberally with carburetor cleaner and clear any passages in the float bowl with compressed air.

Mix a solution of 1 part lemon juice to 6 parts water in a metal pot. Place the solution over a hot plate and heat to a gentle boil. Submerge the entire carburetor and float bowl into the solution and allow it to soak for 20 minutes.

Remove the carburetor and float bowl from the solution and rinse immediately with clean water. Scrub the carburetor with a toothbrush to remove any remaining debris or build up and rinse thoroughly. Dry the carburetor with compressed air, directing the air into the fuel passages to dislodge any trapped water and loosened debris.

Reassemble the carburetor and install it onto the motorcycle.

Items you will need

  • Screwdrivers

  • Container

  • Aerosol carburetor cleaner

  • Compressed air

  • Plastic bags

  • Pen

  • Lemon juice

  • Water

  • Metal pot

  • Hot plate

  • Toothbrush

 How to Clean the Carburetor on a Yamaha Scooter

Place the carburetor into the wash basin, ensuring that the drain hole of the tray or basin is plugged.

Spray carb cleaner into each orifice of the assembled carb, clearing all initial passages of fuel residue and potential debris. Spray the body of the carb as well, to clean any grease away.

Remove the fuel bowl from the base of the carburetor with a screwdriver, taking care to avoid damaging the head of the screws. Pull the bowl away from the carb, preserving the gasket that presses between the bowl and the primary body of the carb.

Spray carb cleaner in the bowl, directly spraying the fuel float and all walls of the bowl. If any fuel residue remains, scrub it away gently with the toothbrush. Spray inside the base of the main carb body, in each of the orifices you see. Again, scrub away any stubborn residue or debris from the main body's base.

Blow the interior components of the carb with compressed air again to remove any stubborn debris, especially from the holes and ports, where small debris can become lodged.

Place the bowl gasket on the bowl and press the bowl against the base of the carburetor. Screw the bowl screws tight with the screwdriver, ensuring the gasket is not pinched or kinked. If this occurs, loosen the bowl screws and properly align the gasket so it can make a tight seal. With the bowl screws tightened, the cleaning process is complete. You'll now have clean carb walls, jets, ports and floats.

Items you will need

  • Cleaning tray or wash basin

  • Carburetor cleaner spray

  • Compressed air

  • Soft-bristle toothbrush

  • Screwdriver

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