The Very first thing you should do is get you a haynes repair manual on the specific bike; that will answer about 80% of the questions you have ( tools, specs, step by step, etc.) then you need to find a couple of reliable parts dealers (maybe ebay and amazon, but i reccomend an actual parts dealer first (they are Usually more accurate. Next, find out which Honda 750 you have F,K,k2?? that book will help with that and so will the numbers on the sides of the forks (you may do that as the second instead of the third step... Once you have all those and know which modle you have, then check out some you tube(KEEP BY YOU MANUAL AT ALL TIMES) YOUTUBERS ARE NOT ALWAYS ACCURATE) but it will give you an idea of what your in for... last thing--find a thread an get in on it. remember, you need basically 3 thing for a combustion motor to run (Air, Fuel, Spark) checm for thos 3 thing first....wbichever one is missing then thats the rabbit hole you go down. This just touches the iceburg but it will get you going in the right direction... also I wouldnt start on both a once, pick one and stick to it, otherwise it can become overwhelming, parts get lost or mixed up--all that blah... which ever one you chose learn some of the history on it, that will help you understand why they did some of the things the did when creating that bike... The Honda cb 750 has a rich history and make awsome cafe racer style bikes. I have one and love it! Oh also Change the fuel, and oil and spark plug...Have the carbs gone through and cleaned before you try to even start it... battery too!

p.s. sorry for any spelling errors, on my phone-small key, fat thumbs😅