Carburetor type BVF 21N1-12 21mm Simson S51

Carburetor for scooters, motorcycles and mopeds

The smooth operation and optimum power output of your scooter, motorcycle or moped depends, among other things, on the carburetor, whose job is to create the right mixture of air and gasoline.

How the carburetor works

When the rider operates the throttle, the carburetor slide moves upwards, increasing the air flow that is sucked in through the air filter. The carburetor then mixes this air with petrol, creating a combustible mixture. This mixture is fed into the cylinder through the intake manifold and the reed valve.

The carburetor is equipped with jets to adjust the ratio of fuel and air and thus ensure an optimum air-fuel ratio. It is important that you adjust the carburetor settings to the setup of your engine.

Adjusting the Carburetor

Proper carburetor adjustment is critical for optimal engine operation and durability. Depending on the type of air filter, cylinder and exhaust of your setup, you will need to readjust main and pilot jets. To check the correct operation of the carburetor, you can refer to the color of the spark plug:

• White spark plug = too lean
• Black spark plug = too rich
• Brown spark plug = optimal setting