Allot of the hubs I’ve seen don’t have enough metal around the stud to make a repair like that viable. Also do you have the ability to get the stud repair perfectly square and on center or are you going to free hand it? Helicoils are not the best imho and I’ve seen allot of them done badly. I use solid inserts when there is enough metal to put them in. I’ve custom made double diameter studs in some cases but, you have to be careful, hubs get highly stressed. I moved away from magnesium parts early on when I saw many cracked components and striped out bolt holes on different karts. I would suggest buying 2 new aluminum hubs.
FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience