the carbs on these are somewhat finicky. also, relative humidity DOES play a factor in how easy they start. Here in SW florida, mine would be a real bear to start, and even let out monsterous backfires now and then when cranking if there was a heavy dew in the morning. My neighbor down the street with a harley has the same problem.
cold starting procedure for mine was as follows (others may vary a little)
petcock on (mine was stock, so it was 'always' on, but the vacuum operated valve in it worked, so it was infact shut off with engine off)
full choke (even if temp was in the 90's, with cold engine)
crank for a couple seconds (usually less than 5 to get it to start)
remove choke as needed to keep rpms around 2k or less
average total time from starting to pulling out of driveway was less than a minute, even on the 'cold' mornings (40ish). actually took more time to push it backwards out of my parking spot than starting, unless it was real humid as mentioned in beginning. if it was one of them days, all bets where off as to what it took to get it going.
will add one thing: if this occurs after engine has warmed up, and been shut down for a few (less than 15) minutes, then need to look at an AGM battery if you dont have one, and the pickup coil mod