Motorcycle carburetor: how to clean it?

Conseils pour entretenir et nettoyer un carburateur moto.

Unlike electronic injection , the carburetor is a mechanical part . It equips a number of motorcycles used for Café racer preparation and requires adjustments and maintenance. Indeed, after a long period of disuse, it is essential to clean the carburetor(s).

The gasoline dries inside the tank, which, combined with accumulated grease residue, leads to clogging of the carburetor and clogs the jets. This cleaning is in fact recommended after the winter break , a significant number of kilometers traveled and of course in the event of a loss of engine performance.

From the role of the carburetor to the parts that make it up, from disassembly to reassembly , discover in this article the advice from our workshop to learn how to clean the carburetor(s) of your motorcycle.

Role of the carburetor

An essential element of the engine, the carburetor controls the air/fuel mixture to ensure optimal explosion in the cylinder liner. Moving down, the cylinder block piston causes air to be drawn into the carburetor. As it passes through the narrowed tube in the center of the carburetor, air flow accelerates, reducing pressure. The gasoline is then sucked up and projected into the air through an opening in the wall of the tube.

This air and gasoline mixture leaves the carburetor through the intake manifold, along the valves, to be burned in the cylinder. In order to regulate the quantity of gasoline sucked in by the carburetor, simply screw in or unscrew the richness screw . Screw in to reduce the quantity of fuel, unscrew to increase it.

Important in the proper functioning of the engine, it is necessary to maintain this essential part. You thus optimize cold starting, idling management and acceleration efficiency. Clogging of the carburetor, inevitable over time, will on the other hand be responsible for a loss of power and torque.

6 carburetor parts to know

Detail of the different elements of a motorcycle carburetor.

From left to right :

  1. choke valve;
  2. idle screw and plug;
  3. the low speed jet;
  4. the main jet : it ensures the passage of gasoline contained in the carburetor tank under the effect of air pressure;
  5. the needle and clip : by going up, it frees up more space for the passage of gasoline;
  6. the needle and its seat.

How to remove the motorcycle carburetor?

Before proceeding with disassembly, make sure you have the necessary tools on hand:

  • socket box;
  • T wrenches, BTR wrenches;
  • screwdriver;
  • cruciform;
  • tweezers.

Enough to work cleanly and clean the different parts

  • gasoline or can of carburetor cleaner, degreaser;
  • rags, wipes , gloves, brushes;
  • container;
  • blowgun.

A carburetor repair kit

Find quality kits from the Japanese manufacturer Tourmax in our online store:

Tourmax kits for motorcycle carburetors available on

The first step is to wash and dry the motorcycle . This will allow you to dismantle the carburetor(s) in a clean environment and not risk adding additional dirt.

Depending on the brand of the motorcycle, the type of engine, access to the carburetor will require the removal of various parts (fairing, saddle, tank, etc.). Provide sufficient storage space to avoid clutter.

Then proceed to disconnect the air filter . Close the fuel inlet valve at the tank outlet then remove the hose attached to the carburetor by a clamp.

Take the opportunity to clean the small fuel filter (if present) at the carburetor fuel inlet. Disconnect the choke and gas cables.

BMW motorcycle carburetor.

Loosen the metal clamp holding the sleeve to the carburetor outlet at the mouth of the engine cylinder head. If the carburetor is secured with studs, loosen them to remove it (use WD40 lubricant if necessary).

Check the suction rubbers for cracks or tears and replace them if necessary.

How to clean the carburetor?

Mikuni motorcycle carburetor. (Photo Old Motorcycle Workshop.)

Pour a little gasoline into a container, place the carburetor there and, using a brush, carefully clean all the exterior parts. (Or use a cleaning spray , let it work.) Then use the blower.

This operation consists of ridding the carburetor of all accumulated residues (grease, earth, dirt, etc.) and thus avoiding the risk of unnecessarily clogging the interior, once dismantled. Complete this step by blowing all parts of the carburetor.

Tip: pay attention to the orientation of the room when using the blowgun to avoid splashing yourself. Ideally, bring protective glasses to protect your eyes.

Motorcycle carburetor.

Use clean gasoline and, still using a brush, clean and degrease the ball and the spring , taking care not to damage the needle.

Once this is done, disassemble the tank by unscrewing the tank nut. Be sure to place the different parts in a clean container and respect the order of disassembly. Then, carefully spray the tank with a cleaning spray. Use a blower and dry with a lint-free cloth.

Dirty motorcycle carburetor tank. (Photo Old Motorcycle Workshop.)

Then replace the tank gasket, taking care to position it correctly without pinching it or damaging it.

Using the tweezers, remove the float and needle without damaging the tab . Then remove the main jet and the idle jet.

Motorcycle carburetor float adjustment. (Photo Old Motorcycle Workshop.)

Unscrew the richness screw located outside the carburetor, taking care to count the number of turns , in order to maintain the same setting when putting it back in place. Next, retrieve the air adjuster spring by flipping the carb upside down.

Clean the holes with the cleaning bomb then dry with the blower.

How to reassemble the carburetor?

Start by reassembling the main nozzle (the number written on it must match that of your kit). If it is not clogged and functions normally, there is no point in replacing it. Do not tighten hard , it is a fragile part, do the same for the idle jet.

Replace the needle at the tab without touching it to avoid disturbing it. Once the needle is positioned on the float, put everything back into the carburetor. Finish by repositioning the rod holding the float.

Place the new spring in the air screw hole then tighten the screw counting the same number of turns as when removing it.

For the needle, follow the same instructions as for the main nozzle, namely a corresponding number. If they differ, keep the original needle to keep the old setting.

Change the carburetor cap gasket then that of the bowl nut.

Screw the bowl nut without forcing then replace the bowl on the carburettor. Screw, leaving a little play while you position all the screws, then tighten.

Reassemble the carburetor on the motorcycle then the cap and the gas cable, the spring and connect it with the bushel. It remains to connect the air filter, starter and gas cables, fuel inlet.

Other topics that might interest you

You will find on our blog different themes covered on Café racer preparations, advice and solutions to carry out your customization project.

Motorcycle Shock Absorbers: 4 Adjustments to Know

How to Rebuild the Electrical Harness of Your Café Racer?


The Old Motorcycle workshop by Breizh Old Motorcycle

A big thank you to Carole and Norbert, from Atelier Moto Ancienne , for the photos provided on the dismantled carburetors. Located in the heart of the Landes, near Mont de Marsan, these enthusiasts will take great care of your old motorcycle:

  • catering;
  • engine overhaul;
  • changes;
  • interview ;
  • etc.

To contact them, go here . Do not hesitate, they are at the top!


1 comment

  • Carole Et Norbert

    Merci beaucoup Julien .
    Documentation bien complète 👍👍

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