Yeah, it can get confusing.
The "P" impulse line ALWAYS is nearest the cylinder. It gets the impulse or vacuum pulse from the engine as it pulls intake into the cylinder. Some machines actually have a barb fitting right on the top or bottom of the intake port on the head or cylinder rather than on the carb.
On the impulse/vacuum pump the lowest/bottom port is the inlet port from the tank or petcock.
The middle port is the outlet to the carb bowl.
The upper or outermost port on the pump's cover is where the pulse line goes to work the diaphragm making the pump do its thing.
Last edited by polman500; 02-06-2019 at 09:39 AM.