What is a Carburettor?
The mechanical mixer that blends fuel and air by vacuum alone, common on older and simpler bikes.
Simplified animation — not to scale.
In plain English
Before fuel injection took over, carburettors used engine vacuum to draw fuel from a float bowl and mix it with incoming air, all without any electronics involved.
“A mechanical cocktail mixer for fuel and air, using nothing but airflow and gravity to get the ratio right.”
How it works
As the piston descends, it creates vacuum that pulls air through a venturi in the carb body. That fast-moving air draws fuel up from the float bowl through calibrated jets, mixing the two before they enter the engine. Jetting has to be sized correctly for the bike, altitude and exhaust setup.
Signs of trouble
- ⚠Rough or unstable idle
- ⚠Fuel smell and possible dripping from the float bowl overflow
- ⚠Hesitation when opening the throttle quickly
- ⚠Hard starting, particularly after standing
£60–£350
Always get a written quote. Prices vary by bike, region, and parts brand.