How to Adjust Carburetor Mixture on a Motorbike

How to Adjust Carburetor Mixture on a Motorbike

Knowing how to fix the poor carburation of a motorbike will improve your bike's performance, and allow you to prevent issues such as problems with the ignition or having the motorcycle engine cut out when in movement.

Periodically carrying out maintenance tasks on the bike will help you reduce the chances of having these problems, but there are many things you can do to improve your motorcycle's performance and prolong the life of the engine. In any case, at we explain how to adjust your carburetor mixture to improve performance.

Steps to follow:

First of all, we must explain what causes poor carburetor performance. When we refer to poor carburetor performance, we mean the mixture of air and fuel in the engine is not right. As a result of a bad mixture, problems such as the motorbike switching off during operation or problems starting up the engine can occur.


The first thing you have to do to adjust the carburetor of a motorbike is to locate where it is. To do this, see the vehicle manual. It is usually opaque and in silver aluminium. Once you have access to it the first thing we will do is adjust the mixture of the lower part. To do this, you must move the screw in the lower part of the carburetor that regulates the air intake.


Now, on the top part of the carburetor you need to find the needle that controls the revs. It is this area that we must focus on when a lack of gasoline is the reason for the poor carburetor performance of the motorbike.

The needle has several positions that go from higher to lower, normally it is on 5 but you should move it according to your needs. This controls the amount of fuel entering the carburetor mix.


Finally, we will adjust the upper part of the carburetor. You will have to open the carburetor float chamber where the float valve is. Inside the float valve there is also a float needle, a needle with a hole through which the fuel passes.


When adjusting the carburetor on a motorbike, we must take into account not only the elements of the carburetor that regulate the air and fuel mix, but also the area in which we will use the vehicle. You should consider criteria such as altitude, proximity to the sea, temperature, etc.


The color of the spark plug is the main indicator of what is causing the problem in the poor carburation of the bike:

  • Light brown: the mixture is too lean, i.e. it is low on fuel.
  • Light brown and black: the mixture is too rich, i.e. too much fuel.
  • Black, dark brown: the mixture is too rich, with a lot of fuel.

As you have seen, the procedure for adjusting the carburetor mixture of a motorbike is not easy and many mechanical skills are required to perform it. With this in mind, if you are an average user it is probably best to go to your mechanic to improve carburetor mixture and your bike's performance.

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