The stumbling on acceleration sounds like a bad accelerator pump on the carb to me. A kit in the carb should take care of that. As for setting timing you can do a search and get hours of reading. Since I don't like standing on my head trying to get the right viewing angle to set it "correctly" I simply adjust to fastest idle with the octane adjuster set at 0. Good luck.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.