Carburettor needle - GY6 50ccm 139QMB/QMA

Carburetor needle

Although it is relatively rare, sometimes you need to change the carburetor needle to fine-tune the carburetor. In most cases, it is sufficient to change the position of the needle to optimize the settings.

The position of the needle mainly affects engine behavior in the partial load range (1/4 to 3/4 throttle).

The thickness of the needle affects the entire rpm range. Thinner needles lead to richer mixture, thicker ones will lean out the mixture.

When adjusting the carburetor, it's a good idea to experiment a bit, preferably ordering a box of main jets (full throttle range), a box of pilot jets (mixture at low rpm) and a box of needles.