19-05-19, 09:08 PM
If the bike is idling it has no throttle input right? If the throttle is closed the butterfly valve in the carb is basically fully closed so no air fuel mix can get through the main circuit so to keep the bike idling with no throttle input there has to be a separate idle circuit that's independent of the throttle. The idle circuit is made up of the pilot air jet that you mentioned, air from the airbox is drawn through that at idle. The pilot fuel fuel jet, fuel is drawn up through that from the bowl and then the air from the pilot air jet and the fuel from the pilot fuel jet mixes and is drawn into the engine. The mixture screw is a restriction in the idle circuit. It sets how much air fuel mix can be drawn through the idle circuit so on the Fazer if you turn the screw in it blocks more of the pilot circuit so that leans the mixture, if you turn the screw out it lets more air fuel mix through so that richens the mixture. The two turns out is two full 360 degree turns out from tightened. You have to be very careful when you tighten the mixture screw because the tip of the screw is very thin and easily damaged.
If you search for "CV Carburetor " on youtube there's a very good animation showing how a carb works. It's about a 2 minute video
If you search for "CV Carburetor " on youtube there's a very good animation showing how a carb works. It's about a 2 minute video