Sounds like you need to fix the stripped stud first. Your best bet is to do what these guys said. Forget about jetting for now. I know you want to ride it, BUT YOUR NOT GOING TO WANT TO REBUILD IT! Fix the stud first. Then look the whole bike over. If the previous owner left a head bolt like that than who know what the rest of the bike is like. I would check every nut and bolt. Also if your running a stock carb there is no need to run that reed spacer. Take it off and throw it in your tool box. Use it when you need a bigger carb. Use yamabond on sealing surfaces. Then do a leakdown test and compression test. Fix the leak if there is one. Clean carb/set float. Then do your jetting. Do this and you will be able to ride with confidence. You have received some very good advice so please follow it. Do your motor a favor and DON'T BLOW IT UP.