Roger - if the originals had been turn-to-lock then the reproductions would be too - never saw one that was, either in originals I've known or parted, or in any brand I drove way back - such a feature would be an accident waiting to happen in a panic situation!
the "safety feature" of the return spring is it keeps the linkage from flopping to full throttle when you get past a certain point - the problem w/ the linkage in regard to the hand throttle is the spring tension may no longer be just as designed, 50 years later, or your cable may be weak
also note that the primary purpose of the hand throttle was for operating PTO equipment that required higher than idle engine speeds, NOT as a 'cruise control'
Bill
