Motorcycle Repair: Kawasaki 1994 VN1500 backfiring/popping, vroc vulcan, drifter 1500

Question
Can you please share your thoughts what could be causing a backfire/popping in a 1994 Kawasaki VN1500A 88?  Some symptoms I noticed are:

1) Appears to be only the front cylinder.
2) I see a glow in the first cylinder exhaust pipe when the popping occurs.
2) No popping until warm.  Definitely more prevalent when the bike warms up
3) While at an idling stop, more prevalent when I lean the bike to the right, not so much, if any when I lean the bike to the left.
4) All plugs and caps changed out.

Thank you for your time and thoughts!

Best Regards

Answer
Do you have a low restriction aftermarket exhaust or stock mufflers? Any changes to the air intake system (low restriction air filter, jetting, etc)?

Unfortunately, I have very little experience with Vulcans except for the '99 Drifter 1500 I owned a few years ago. You should ask your question on the VROC (Vulcan Riders and Owners Club) as they have a large membership base and an excellent forum: http://www.vroc.org/