A few thoughts:
(1) I was unaware that Fenton made carburetors, so no comment on how to hook to the carburetors.
(2) Some carburetors (notably those originally on MoPar products) have the internal accelerator pump spring designed so that the carburetor (without a return spring) is at half throttle! Anytime MoPar carburetors are used, the throttle return spring(s) must be significantly higher in tension to overcome the internal accelerator pump spring(s).
(3) If both carburetors are using chokes (and I highly suggest that they do, MUCH better low end torque by using the choke butterflies as "straightening vanes"), if one of the chokes is not at the maximum opening, an idle screw could be on the second step of the fast idle cam.
(4) I have yet to see aftermarket linkage that I personally like, and make my own, which is much heavier than the A/M stuff. Mine doesn't bind. No, I don't make it for others, don't ask.
(5) We have ALWAYS used a return spring on EACH carburetor. Having a spring on the linkage may never cause all carburetors to return to the idle position.
Jon.
