33 CFR §183.526

1. (a)[Reserved]
2. (b)Each carburetor must not leak more than five cubic centimeters of fuel in 30 seconds when:
   1. (1)The float valve is open;
   2. (2)The carburetor is at half throttle; and
   3. (3)The engine is cranked without starting; or
   4. (4)The fuel pump is delivering the maximum pressure specified by its manufacturer.
3. (c)Each updraft and horizontal draft carburetor must have a device that:
   1. (1)Collects and holds fuel that flows out of the carburetor venturi section toward the air intake;
   2. (2)Prevents collected fuel from being carried out of the carburetor assembly by the shock wave of a backfire or by reverse air flow; and
   3. (3)Returns collected fuel to the engine induction system after the engine starts,