WEBER 40 DCNF COLD START/FAST IDLE MECHANISM

I've attached a picture of my 76 European 308 carburetor set up. There is a mechanical arm that contacts a an irregularly shaped cam like mechanism that I believe is part of the cold start and fast idle system. I'm not entirely sure how it should BE SET UP AND I'M WONDERING IF SOMEONE CAN GIVE ME SOME DIRECTION AND WHETHER OR NOT IT WOULD HAVE ANYTHING TO DO WITH SETTING UP THE SYNCHRONIZATION OF THE CARBURETORS WHEN FULLY WARMED UP. I WOULD THINK NOT, BUT I WOULD LIKE SOME EXPERT HELP.
THANK YOU VERY MUCH

STEVE MELTZER.
(ADD: not sure why part of this request came out in all caps, I ain't typing it.) s
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Steve,

It is the cold fast idle mechanism. At the bottom right of your circle, the red line passes through the adjustment screw for the cold fast idle. There is a thermostatic spring in the housing that rotates the cam as the coolant warms that in turn moves the lever and pushes on the throttle linkage.

From your picture, it looks like you snapped it when the engine was warm as the flat side of the cam is at the lever. Also the fast idle adjustment screw at the throttle linkage is backed all the way out, so even when cold, the fast idle mechanism would not come into play.

The way it is set now is the way it should be when synchronizing the carb throttle linkage. Once your linkage and 2 main idle stops are set correctly, you COULD crank down on the cold fast idle screw to have the function operational. Most people however disable it the way your picture shows because the cam lobe can stick and if it does, you are stuck with a fast idle.

 

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THANX SO MUCH DOCKBOY! MUCH APPRECIATED. s

 

Steve,
I'm no expert here, but I do happen to be in the middle of overhauling my throttle linkage at the moment. I had horrible stiction that would delay the throttle closing for a good 2 - 3 seconds and finally traced most of the problem to (what is probably) 46 year old grease in the throttle linkage pivot's needle bearing.

But in the course of stripping the linkage, I too had the opportunity to ponder the fast idle device. Even though I had no idea it held cold idle at 3,100ish RPM until I read Dockboy's post, I knew just by looking at it that I was going to disable it. It just seemed like something else ready to fail - like the choke mechanism - and not do my engine any favors when it did. Best of luck with your project.
- Dave