Talk about obscure... This is a carb for an old track speeder. The engine is a big slow-turning crankcase-scavenged two stroke engine. The float-type carburetor is simple, with choke and just one adjustable main jet. No throttle but are there not one but two vacuum-activated poppet valves in the intake tract. Anyone know (or have any guesses) why this arrangement? It appears the speed is mostly controlled by the spark advance.