I'm pretty sure I used a 2/56 bolt on the throttle and a 4/40 on the choke. I know I did not drill out he hole. Either a 2/56 or a 4/40 fits that throttle level. I can't believe how nice that DA85 is. Its my first DA. Started right out of the box, haven't touched the needles and it just purrs. Expensive yes but nicest motor I've owned.