It's not all about slack.
I took some time today and looked at the idle motor, throttle valves and cables. I think I understand the need to command the idle motor to release the throttle valves. Please take a look at the pictures and video and comment if I'm on the right path.
When adjusting the throttle grip free play we can do it using one of the two adjusters in the front or on the rear throttle cable. The problem seems to be that if we adjust the return (front) cable too short we can resist the idle motor and prevent it from opening the throttle enough for correct idle. The front cable must be long enough so that pushing the grip backwards it stops on the resistance point in the grip itself.
You can see on this video how with wrong adjustment the idle motor transfer movement on the grip.
So the idea is to shut off the power when the motor is in it's test cycle and stop it on its disengaged state. Then adjust the throttle so that we cannot pull the bottom (return) cable when twisting back the throttle grip.
Here is a video how I think we can do that. Sorry for my bad English.
PowerCell, what do you think? Will this do the trick?
I'm attaching a picture with the wrong adjustment that puts force on the idle motor.