I'm deliberately using this as a platform to respond from, as it comes from someone who knows about the manual and has actually looked at it.
Good on you, Sir !
Well, what I consider a tower where an air screw would be, could you look under the t-body with a mirror, show where there are none and the book does.
Unless that picture is deceiving in the manual.
There are no idle air screws on the 919.
I have a closed looped bike. It has it's own idle screws.
1. One hole ~ Is for the intake air pressure sensor.
2. Hole two ~ Is for the idle air screw.
3. Third Hole is the fuel pressure regulator (if applied)
Are we catching a 3-ring circle?
1. Fuel - Spark - Compression = 3 ring circle
2. Solid - Liquid - Gas = 3 more amigos
3. Breath in - Hole your breath - Exhale = Ding-Ding-Ding! 3-Have a winner!
The enrichment circuit is manually actuated by the pull nob when intended, but is controlled by starter valves.
This circuit is inoperative unless the nob is pulled.
I'm the thick one here. I get confused easily. What you are saying is, this is a choke that has to be used when warm also? Or, are you saying this is only for morning start?
The starter valves are factory set, with 3 being adjustable and one being fixed.
Say hello to my nu frien. Put two and two together. "This is my rich valve (always sucking fuel out). I'm going to close some fuel down." If I am in the opposite, meaning, air screw hole, I am now a fuel hole. I am either or... Who has a grasp of the t-body here? Do we know where there is fuel plumbed to this adjustable air screw that is fixed? Get it? The one screw is fixed. We are looking at a throttle plate, not an air screw that is fixed to shaft. That is the main plate you balance with the loss of some compression on the other cylinder. That is the first thing you do before you set the valves or sync is to check compression or you over bleed the vacuum to a poor or low compression cylinder = Poor idle.
One can revisit the settings of the 3 adjustable units through the life cycle of the engine, and the adjustments are made on the basis of getting the vacuum readings all the same.
Again, this circuit is inoperative unless the nob is pulled.
You mean, set this in the tuning loop, in other words. Yes?
There are no Idle Air Control screws on the 919's F I system.
However some other Honda's do have Idle Air Control screws on their F I systems, a good example of this being the GL1800, which not only has such screws on the throttle bodies, but also has a car like Idle Air Control valve that is electrically energized and manipulated by the ECM.
Either FI runs with those 3 variable holes or I'm getting schooled by Honda's engineering dominance. A GL has 3 variables with the IAC systems, but the 919 has eliminated a 3rd hole and no one has yet to show the venturi passage for the 2 hole combo.
Unless an external device such as a PC is attached, or the starter valves are actuated, it is impossible to change the ECU controlled fuel metering under any engine mode, be it cold start and idle, or hot full throttle.
Again, that cold start is for...
That passage is like air passage where homehee don't need no choke if we tell the water it's hot the watt the hack attack.
The throttle blades are factory set, and there is no instruction on how to adjust them. Mr. Honda does not want any of us messing with this. IF they were to be adjusted, perhaps as a result of someone ignoring the warnings about the painted screws, then some set screw would have to be tweaked in response to a vacuum gauge.
See, we are going back and forth here between air screws and IAC screws. This is still a tuning tool where homehee don't need a pc.
There is a reference to Idle Valves.
I do not know if they mean a dedicated set of Idle Valves, or if it is a manual error and Starter Valves is correct.
In other words, there might be a dedicated set of Idle Valves in addition to the Starter Valves, but I don't think so.
And the Starter Valve settings would be messed up if the Throttle Blades got out of synch.
Are we catching all this yet? You are explaining all this to me and I am confusing you so it makes absolute sense. I cannot see one less vacuum hole in the scheme of FI.
Dev is correct re some F I systems having screws air, but 919s are not in that category.
And, any such screws are for idle control only.
They may not be in that category, but if fuel enters in the constant or air enters in the constant, do we have a tuning out of some richness without a pc, yes or no?
And the air cleaner deal. Did we notice how we become rich with a dirty air cleaner? If we want to destroy our cylinder walls, then we run a racing air cleaner, let some air come in on the leaner side, we remove some stock pipe and that moves some air in there too.
3 variables without pc:
1. Stupid move, but no air cleaner is leaner.
2. A nice loud pipe to add more lean.
3. The air or fuel screws and more air is lean, or close the idle down or off is the leaner machiner.