Carburetors are complicated mechanical contrivances, and can be difficult to understand for the uninitiated. They’re often explained with teaching resources like cutaway drawings and diagrams that reveal the magic going on inside. Even better would be to look inside as it’s all happening, and with the transparent carburetor from YouTuber Smarter Every Day, you can do just that.
The video came about when Destin Sandlin, the man behind the channel, asked his father to explain to him how carburetors work in practice. This inspired him to build a transparent carburetor so that he could literally see what was happening inside. The device was built using a transparent resin 3D-printed housing for the bowl and venturi, and fitted with a float and needle from a Briggs and Stratton carburetor. Throttle and choke were then installed, made from 3D-printed PLA plastic. The clear carb was then installed on a small single-cylinder engine on a Craftsman garden tiller.
The principle of operation is simple. Fuel from the tank flows into the bowl, raising the level of the float as it does so. As the fuel in the bowl gets higher, the float does too, until it closes the needle valve which stops further fuel flowing into the chamber. This mechanism maintains the right level in the bowl as fuel is consumed by the engine. Atop the bowl sits the venturi tube, connected to the intake of the engine. As air is sucked in through the venturi by the engine’s intake stroke, it creates a vacuum, which sucks fuel from the bowl into the venturi tube via a small hole called a jet. It’s by this process that the fuel is mixed with the incoming air, to create the combustible mixture that then burns in the cylinder on the power stroke.