Check your choke cables/plungers. I had one working and one stuck. Similar symptoms to those you describe. Other than that, drain float bowls (could have crud in there), check carb/inlet rubber/cylinder head joints. Check the little balance stubs on the carbs have rubber caps on. Have a look at your vaccuum pipe to the petcock too!
Good luck in fixing it.
Anybody know why my bike's not charging?
Regards
Rich