I have a 170 and examined the linkages without actually taking anything apart. There is a spring which connects between the lower part of the governor arm and the throttle bracket assembly. The governor arms connects directly to the carb throttle with both a solid link and a long thin spring which takes up any slack in the solid link. These connect to the top of the governor arm.
When you raise the throttle lever on the dash, the cable is connected to the mechanical assembly (throttle bracket assembly) and causes it to rotate and pull on the spring connected to the lower part of the governor arm, thereby increasing engine rpm.
Does this sound like the spring you are referring to?
