What's the difference between a plunger throttle and a horizontal carburetor? Are they interchangeable? ...

Both structures are self-priming carburetors, but the structures are somewhat different. The former depends on the opening and closing of the plunger to control the air intake, and at the same time, the oil needle of the main metering hole is lifted to control the air intake. The latter should be a rotating valve plate structure, which controls the air intake only by the opening of the valve plate and by the air intake. Motorcycles use these two kinds more. The former is easier to maintain and more widely used at present, while the latter is more difficult to maintain, but relatively more fuel efficient than the former. As for the exchange, it is difficult.