English: Detailed inner working parts of a Keihin PB carburetor

A - throttle cable tube
B - throttle slide housing
C - venturi tube air inlet
D - choke plate, to ease up cold start by blocking the air intake, which will pull more fuel from the pilot jet as the result of vacuum of air inside the system
E - throttle valve (slide type), regulates air portion of the mixture
F - throttle needle, attached to throttle valve, regulates fuel portion of the mixture
G - pilot tube air inlet, a smaller venturi which enable pilot jet to supply fuel to the main venturi
H - fuel bowl, contains the fuel
I - fuel drain screw, for draining the fuel from the bowl
J - fuel drain hose
K - needle valve, attached to the fuel float, regulates fuel entering the bowl
L - fuel float, closes up the needle valve when the bowl is full
M - pilot jet, supplies fuel at idle and low throttle opening when the throttle needle closed
N - main jet, supplies fuel at a higher throttle opening, when the throttle needle is high enough to let fuel properly mix
O - fuel inlet, connected to the fuel tank
P - choke lever, controls the movement of choke plate
R - throttle slide spring, keeps the throttle slide at normally closed

S - venturi tube air outlet, supplies fuel-air mixture to the combustion chamber