Yes, Good that it is out.
The vice thing is because they can easily be fcuked if you are not used to working with them. Your mate might have used some fibre jaws or bits of plywood to protect the carb though!
Now the important thing. Don't use carb kits! Often, you can re-use everything that is in a used Mikuni, apart from the Main jet and the Pilot jet which should both be replaced with new gen Mikuni because you cant tell if the Main has been modified and the Pilot is small and often has corrosion or muck restricting it. Check the Needle under a magnifying glass, if not worn or bent it is good if the right part. Check the Needle jet is clean and inspect the opening hole with the magnifying glass. If it is undamaged and the hole is round with no wear to make it egg shape, make sure it is the right number and that is good. The Float needle should not have a wear ridge, a slight mark is OK, and they need the spring pin freeing-off and the brass body needs polishing inside with solvol autosol on the end of a wound rag. The Air corrector feed passages from the floatbowl big nipple to the Needle jet emulsion tube needs to be checked clear with air, and "balls-out" treatment done if blocked.
The thing with carb kits is that they are not as accurate as the genuine Mikuni parts. If your Needle, Needle jet and Float needle valve are good, you only need new Main and Pilot jets and they are about £6ea, so about £25 for a full new gen Mikuni set.
Overall, good carb rebuilds are not just fitting a new carb kit. They need careful inspection and cleaning, checking every single part is correct, cleaning all passages completely and sympathetic assembly with Mikuni parts.
Cheers
5port
