The original owner who put on the pipes and new air filter was a mechanic at a Harley dealership, so I'm guessing he correctly adjusted the carb with new jets or whatever else was required.
I've owned the bike for well over a year. Until this week, I never had a problem starting it. So, it's not just a matter of getting to know the quirks of the bike; something changed.
I have a friend who can help me next weekend. We'll pull the bike apart a bit and figure out what's going on.
Consensus here seems to be that it's a fuel mix issue, so we'll start there. And Jack's link with the carb info seems very helpful.
Thanks.