The RBS (round bowl single) carburetor is made up of a single aluminum casting with pressed steel fuel bowl.
Fuel pick-ups are located near the center line of the carburetor bore to gain the benefits of a concentric bowl carburetor, yet so located that engine heat being radiated through the carburetor bore and conducted through the casting is not readily conducted tot he fuel in the fuel bowl.
The RBS is an air bled design using a “downhill” nozzle. Hot operation must be a very important consideration in the design of a carburetor.
To maintain the carburetor bowl temperature at a minimum for summer operation while applying heat to the carburetor flange to prevent icing in colder weather necessitates a compromise in design. This compromise has been minimized in the RBS by suspending the metering system and accelerating pump. These important areas hang into the fuel which is contained in the rapid heat dissipating sheet metal fuel bowl.
There is no direct contact of the metering points with the bowl because of the isolation features. The fuel passages of the conventional carburetor are usually in the bottom of the bowl which is subjected to conducted and convected engine heat. Vapor vents allow rapid dissipation of gasoline vapors to assure smooth idle and to minimize hard starting while the engine is hot.
The RBS is made up of five circuits
- Float circuit
- Low speed circuit
- High speed circuit
- Accelerating pump circuit
- Choke circuit