Hmm sounds like my bike but only happens during a long time sitting like for weeks without being started. How long does it sit for before you usually start?

Backfiring during a start sounds violent. I only get that after weeks of not riding it.

 

The wife's stg1 '08 Low Rider would rarely kickback when the starter was hit, always after fueling up in 100+ heat. If the starter was tapped, then held down, it wouldn't happen. I eventually had S&S E-Z start 551 cams put in and it's "E-Z" starting every time without all the $$$ up-sell of batteries, cables and starters. A friend has an '06 Road King he's punched out to 124" and he uses the stock 88" starting system with the S&S E-Z starts...
If your bike has factory comp releases, maybe they're sticking or not functioning properly??

 

Let me tell you what I found. It may or may not be anything. But today, she did NOT backfire.
I pulled the plugs and found NGK resistor plugs of the wrong number for my FLD twin cam.
They were not the DCPR7EIX Harley says to use on the FI FLD Dyna.
They were DCPR7E.. To me, that's the same plug. But NOT iridium.
Anyway, wondering about a possible fouling issue or an issue with an internal resistor, I swapped out for a set of DCPR7EIX.
The original plugs did not look fouled. But the bike did not hickup or backfire on me today.
I rode about 75 miles and shut down and re started several times.
Maybe it's a fluke? Or maybe I had a funky sparkplug?
I'll update soon.

 

Interesting...

 

I had a trickle charger on the bike and the house was hit by lightning. The charger is dead and when I checked the battery on my bike it was dead as well. I recharged it and it held the charge but when I went to reattach the bike to the battery....the starter started turning over. Is there a starter relay that is separate from the starter I could look at? any other idea what would cause the bike to do this. The ignition switch was in the OFF position.....

 

There is a starter relay- look it up in your owner's manual. But probably not the issue.
If you battery was completely dead it may be damaged and not able to be recharged. Get it charged up and have it load tested.

 

It sounds like the contacts in the starter solenoid have welded (stuck) together.
The solenoid is relatively cheap and easy to replace.
I suppose a large electrical surge could've done that.

 

An update:
I've been riding the HELL out of the bike trying to determine why it vibrates so harshly above a certain speed or RPM.
I didn't find out why.
But I DID FIND that it hasn't backfired even once since I changed the plugs to the new, correct type.
It starts like it should, now.

 

I remember a similar post about a year or two ago. the consensus then was, when the engine is hot the start circuit needs a couple more rotations on the crank to read the signals and signal the ECM for a hot engine start. I've learned on my '02 that if I release the start switch too soon on a hot engine I will get a backfire through the carb and a ton of smoke, if I allow the engine to spin a couple more revs. all is will, same on my 2013 103.

 

I also had a problem with hot starts and it had stock spark plugs installed. My opinion, is there isn't enough oxygen in the cylinders, after the pump primes, to support combustion. That's why I always turn the stop/run switch to run, before I even turn the ignition on. Turn the ignition to on and immediately hit the starter. It has worked for me every time for years now.
If you had either manual or auto crs then your problem may lie in a different area. My small bike has manual ones and I always open them right after I shut down the bike so they don't get heat soaked for the next hot start.