G-11, built Sept. '06. 80K+km. Throttle stop "sacred screw" turned down a long time ago, causing wear, and prompting "new" throttle bodies (e-bay) with only 12K miles. Like new, wit all yellow paint intact. (See "Ask The Wrench" recently)
I measured the throttle plate at 5.7 mm, quite high compared to the 4.8mm I have worked with in the past.
Installed, the bike rumbled to life and settled quickly into a 1250 rpm idle. Wow!
Test ride a few minutes down the road....idle now at 2300! Back home, isolate the stepper motor, try again. Now idling at 1700.
So I go back to what I know: set the throttle valve at 4.8 mm, and re connect the stepper motor.
Motor settles into a slow (900-1000 rpm) idle, slowly creeping up to 1150-1200 as it warms up. It is consistent here, but I do not get the brief high idle on a hot start. Over time I raise the hot idle to 1250. The bike runs fair, but something is amiss.
Then it hits me: the stepper motor is not getting enough air. I pull the hose off the spigot on the airbox and go for a ride. WOW! 1250 idle hot and cold. A brief excusion to 1900 rpm on a hot start.
Investigation finds the fitting on the left side of the air box is quite small. Inside the airbox there is a 90 degree downward elbow, much like the one on the right side that draws oil fumes from the breather box. There is no way this little opening can supply the air needed when the stepper valve is fully open for a cold start.
So I remove the airbox, and run a 15/64" drill from the outside in, right through the elbow into the forward chamber of the air box, same size as the large intake port on the stepper motor.
Here the airbox is back in place, but it shows what I mean. All has been right since I did this.
The following is my own interpretation of what may have happened:
At the end of the assembly line, the bike is started up and the idle set to 1250 followed by the TPS re-set.
The stepper motor set-up is proven enough that there is no need to go to full operating temperature, and sync may already have been done by Weber on a flow bench.
Since the airbox can not supply the air needed with the stepper motor in max air mode, the throttle valve is inadvertently and unknowingly set too high to accomplish the 1250 idle speed, with the assembly line workers just following the instructions from the engineers.
When the bike later is fully warmed up by it's new owner, the throttle is set way too high, and the throttle stop screw is "untouchable".
When the stepper motor valve is in the min.air position at operating temperature, that little orifice supplies enough air to keep the balance, which is why my bike eventually found its way up to 1250 rpm when set at 4.8mm before I did the surgery.
Go ahead, tell me I am crazy!
I measured the throttle plate at 5.7 mm, quite high compared to the 4.8mm I have worked with in the past.
Installed, the bike rumbled to life and settled quickly into a 1250 rpm idle. Wow!
Test ride a few minutes down the road....idle now at 2300! Back home, isolate the stepper motor, try again. Now idling at 1700.
So I go back to what I know: set the throttle valve at 4.8 mm, and re connect the stepper motor.
Motor settles into a slow (900-1000 rpm) idle, slowly creeping up to 1150-1200 as it warms up. It is consistent here, but I do not get the brief high idle on a hot start. Over time I raise the hot idle to 1250. The bike runs fair, but something is amiss.
Then it hits me: the stepper motor is not getting enough air. I pull the hose off the spigot on the airbox and go for a ride. WOW! 1250 idle hot and cold. A brief excusion to 1900 rpm on a hot start.
Investigation finds the fitting on the left side of the air box is quite small. Inside the airbox there is a 90 degree downward elbow, much like the one on the right side that draws oil fumes from the breather box. There is no way this little opening can supply the air needed when the stepper valve is fully open for a cold start.
So I remove the airbox, and run a 15/64" drill from the outside in, right through the elbow into the forward chamber of the air box, same size as the large intake port on the stepper motor.
Here the airbox is back in place, but it shows what I mean. All has been right since I did this.
The following is my own interpretation of what may have happened:
At the end of the assembly line, the bike is started up and the idle set to 1250 followed by the TPS re-set.
The stepper motor set-up is proven enough that there is no need to go to full operating temperature, and sync may already have been done by Weber on a flow bench.
Since the airbox can not supply the air needed with the stepper motor in max air mode, the throttle valve is inadvertently and unknowingly set too high to accomplish the 1250 idle speed, with the assembly line workers just following the instructions from the engineers.
When the bike later is fully warmed up by it's new owner, the throttle is set way too high, and the throttle stop screw is "untouchable".
When the stepper motor valve is in the min.air position at operating temperature, that little orifice supplies enough air to keep the balance, which is why my bike eventually found its way up to 1250 rpm when set at 4.8mm before I did the surgery.
Go ahead, tell me I am crazy!