From my experience with the 1983 honda shadow it is very cold blooded. If it turns over well without diming the dash lights (possibly indicating a bad ground or other connection) and you have good spark at the plugs I would pull the carbs and rebuild them or atleast thourghly clean all the jets and the choke mechanism. I have found that if you choke the bike a little and try to start it then wait a minute or so then try again it will usually fire once or twice. Repeat this sequence until you can keep it running and then choke it more for a while until its warmed up good. Also try running a lille carb cleaner in the gas if you dont want to tear into the carbs just yet. good luck!