CODE RED CARBS

hello all.....
you guessed it, i have cracked into cleaning the carbs, i have read alot of posts here regarding cleaning, and found a hugh amount of help. I like to consider myself a DIYer, with sites like this one, pretty much anyone can fix an XJ.
Here's my dilema..... i purchased this bike last summer from a guy, who obviously NOW i realize did not take GREAT care of the bike. oh.. but I have big plans later for this sweet little machine..... lots of info and ideas found here of course. anyway, as i started to remove the mixture screws, i noticed that 2 were in good shape, 1 had the wings starting to turn and the 4th is totally FUBAR'd, i fabricated a perfect fit screwdriver from an old one, fits snug as bug, to get the 3 good looking ones out, worked perfectly, so now i am in a bind for the last one..... i read and printed some info regarding cleaning out around the screw then using a screw extractor to get it out, tried it last night and i think i may have made things worse, i may have struck the side wall of the carb body, and now afraid that i may not be able to back out the screw at all........
My only question at this time is - if i drill out the screw entirely, will there be enough carb body to re-tap, and what size of tap is needed?

 

Stop. . . Use Kroil. . . get some Kroil.
Use heat even. Last chance is an easy out.
I don't think anyone but a machine shop could re-thread or heli-coil that, it's precise and a rare metric thread too.

Or shop for a spare carb body.