1983 Yamaha 30EN Outboards Service Manual, Page 43Get this manual
4 Flows of fuel and air (At wide open throttle) At wide open throttle, the fuel metered by the main jet is mixed with the air metered by the main air jet in the main nozzle, and the resultant mixture is suck-
ed into the main bore where it is vaporized by air streamsNote that even at open wide throttle, mixtures are supplied through the pilot outlet and bypass holes in the low speed circuitJ