Can't, bought them like this, knew about it...I would make the machinist fix it. HE should have known better. Like FIRE-MEDIC said about using a left hand drill bit. You can get a lot of stuck or broke bolts etc. out with them. As far as your carb goes you cannot tap it out larger so i would have the machinist turn down a peace of aluminum just about one thousand larger than where he cut out and press the pin in and there you have a fresh start for him to center it up and make things wright where he made a mess. something to think about.
Not annoying - as stated above these are a spare set. I was faced with the same issue with the vmax at the start of the summer, but I left it alone for fear of cocking it up, then waiting for a fix...I've just had a quick search for mixture screw and it has a very pointy end. The replacement thread needs to be very precise for the screw to fit properly.
I'm sure the hole can be opened out for a brass insert to be threaded and pressed in and then drilled precisely before being tapped.
The matching would need having the carb body clamped so everything is lined up.
The threads on these types of screw are fine so it may be fun finding the right tap.
You'd be looking at £200-300 for a set of s/h carbs, set of 4, I've not seen them sold separately.
Else search carb repair, quite a few companies pop up, worth contacting them for a quote.
It must be really annoying that such a small thing has rendered the bike unusable and gonna cost a fair bit to fix.
Update since yesterday - semi successful, I drilled the carb, made an insert, just it was not tight enough in the carb. So will make another 3 thou bigger, should do it.That's what should have been done - but someone drilled the screw and the threads out...
Got the taps today, will spend an hour or two tonight seeing if I can jig it all up to drill out for an insert.
If it all goes wrong I could always make a new insert taking the whole lot out , then drill the plug out of the end and replug. Bit of a faff, but these are a spare set I bought because I have the exact same issue on the ones on the bike - but I haven't drilled that one out yet.
A couple of things this proves:Fitted the odd set (bought on ebay as a set, but the seller had replaced two), with the repaired mixture screw thread today. Had bench synced well enough to run and idle. So I set about with a set of gauges to balance and adjust mixture. I got what I thought was a reasonable idle, but thought they were all a little insensitive to the mixture screw setting. Anyway, it got dark and I put it away. That's when I noticed I hadn't fully pulled the richener lever closed..