My 1978 Columbia Commuter with a Sachs engine and a Bing carburetor has this characteristic: once up to full speed (currently 24-25 mph), laying off the throttle does not slow it down at all. Only the brakes slow it down.
As it slows down(by braking), the 2 speed automatic transmission does downshift to first, but I can't take either brake off or it will shoot forward.
Is there supposed to be some linkage between the throttle and the butterfly valve? Or does the trottle cable only control the carburetor jet?
I can add that it gets pretty poor mileage for a moped-probably only 20 to 25 mpg.
Thanks for your suggestions.