Did you compare the old cable with new? Same diameter and length? What was wrong with the old cable? Did you try lubing up the original and you still had problems? My '65 danced a lot when I first got it. Lubed up the cable and all good.
If it's a repro cable, you definitely can't trust that it's the same as original. Seems like if it worked before and all you did was change the cable, either the cable diameter is different and not engaging the gear or the cable's not in the gear.
Wally,
Did the binding occur from the get go or did it get to a certain MPH and hang?