Carburettor

It was standard on petrol engines before electronic fuel injection. Calibrated jets meter the fuel for idle, part load and full load. Classic cars, motorcycles and small engines still use carburettors. Rebuild kits with gaskets and needles are available for many models.

Air speeding through the venturi lowers pressure and draws fuel from a float chamber into the air stream.

Old fuel evaporates and leaves deposits that block small jets. Adjustments such as idle mixture should be made carefully with the engine warm.