I understand your points, but as I mentioned, I did this exact repair to a 1100 throttle shaft - with **thinner** bushings than in the weber choke shaft, I just did not take any pics and I sold off the 1100 carb a few years after doing this repair when I finally got around to installing the Weber. Because I have multiple drills and reamers, I may have used the next size up drill bit or a reamer to "round" out the hole prior to installing bushings - from experience, I have learned that the higher the speed when I drill the more round the hole (and while my drill press is a marginal Sears unit, it does spin up to 6,000 or so - based on the drill size, I guess that I actually drilled the casting at about 3000). My concern has always been cracking the casting with too large of a press fit on the bushings although with a thin wall, they tend to collapse (shrink in ID) when they are pressed in.
On a couple of occasions I have had a stuck accelerator - either by floor mats or by carb linkage binding. My thought is that there is a risk of the throttle shaft binding if it is not perfectly straight and that is where I would have concerns w/ building it up. Since this is being done to a scrap part, you are not risking much.
If this works out (building up the shaft) to your satisfaction, please report back & pictures would be nice - always willing to learn a new trick (and I already have some silver solder on hand ).
On a couple of occasions I have had a stuck accelerator - either by floor mats or by carb linkage binding. My thought is that there is a risk of the throttle shaft binding if it is not perfectly straight and that is where I would have concerns w/ building it up. Since this is being done to a scrap part, you are not risking much.
If this works out (building up the shaft) to your satisfaction, please report back & pictures would be nice - always willing to learn a new trick (and I already have some silver solder on hand ).