I own a 2014 Superglide 103 CI. Today when I was riding from work, 80 degrees outside temp., it started backfiring when I down shifted, and losing power in 6th gear. I went to another job site and when I was coming home from there, outside temp 65-70 degrees on hwy., it began losing power so much that I had to ride in 5th gear at 55 mph, and then 50 mph in 4th gear until I got home. It sounded horribly at 20 mph like I had a bubble maker, like it was running on 1 cylinder, and I coasted into the driveway. It has 13,500 miles on it and I have babied it, changed the oil at 3-4k miles, run premium fuel, etc... Help!

 

Is it stock or have you changed the intake, exhaust or tuner?
How do the spark plugs look? Are the wires tight on the coil and plug leads?
Check for codes.
Make sure your battery cables are tight and clean at the battery and the ground.
Check for intake and exhaust leaks.
You could also have a hole in the fuel tank line. With a low fuel level in the tank, hit the run button and you can hear if there's gas spraying against the tank wall. Might even be able to see it.