Hi Chris,

I remember one mistake I made when installing the throttle linkage (on the SP series, however): The barrel in the carb has some axial play. When the barrel rotates it moves out and in a few milimeters. A spring inside pushes the barrel outwards. What happend to my engine after throttle linkage installation was that the stiff rod pushed against the barrel axially, against the force of the spring. At certain rpms (in my case at the low end) the barrel vibrated in and out thus changing mixture uncontrollable.

If the CD series have the same habit as the SPs and reach max. rpm just before the barrel rotates fully open I believe Walts posting is number 1 solution for your problem.
If the problem persists, I suggest to check the throttle linkage


regards
Andi