O.k. now I get that 'grind off the plate screws' thing. That is a b*stard act to tamper proof a carby, I have never seen a Mikuni with a guard mounted to it like that... It was really out of adjustment if you needed to bump the choke butterfly gear 2 teeth to get it back into working condition! And it is a rare occasion where you can pull any screw off a Mikuni without chewing the head out of it - they are locked in pretty tight. But it looks like you have defeated the beast - good work