That is exactly what mine does and it has 40K. A few year old take off exhaust off a Nightrain with the oxygen sensors pluged since my 04 did not have them. They do have two .312 holes drilled in each center baffle for a little raspy cam idle since my engine is stock. That and a boot leg SE timer cover gets at least 40 extra HP.? (HA) Has done it for a long time and sometimes annoying loud since I use to leave work at 12:30 AM. A bar across the street one night had a lot of police on site do to some problem and two officers were standing on the corner looking down a dark alley. All I wanted to do was get out of the area and I fired the old boy up and BANG! The two officers jumped 2' straight up. They sure had a good since of humor since they looked over at me shaking there hands and head laughing.
Any way I checked the injector for any drip at shut off and there is non. My compression is perfect so I know no valves are leaking. My plugs look great even after 10K on them pulling them after a 20+ mile run on the interstate. What I think and why it only happens randomly is dependent on how the engine position of the pistons ended on the last turn off. If mine stops on the start of a compression stroke I always get a slight grunt almost like a bad battery and I know it's good since I keep a close eye on it checking and a maintenance charger it my rids get more then a week apart. However if it on the down stroke and it cranks freely and it does not catch on the first firing cylinder I think this fuel injection dumps into the header pipe and the next firing cylinder ignites it with the pop. Basically its just the perfect air to fuel ratio to explode. I do not think anything is wrong personally.

 

Thanks, but the comment I made on the butterfly is not correct for the throttle bodies now, I removed it from the post above were you grabbed it. Was in the past and some cars I have worked on. However Harleys' throttle body has a area open when at the factor set stop that allows a calibrate amount of air to flow beside what the IAC does. Probably to ease tolerance in production and prevent butterfly sticking even at high mileage.

 

I understand that the IAC is responsible for a fast idle on cold startup by allowing more air. If the engine is backfiring on occasion hot/cold, then I'd almost rule out the IAC. I'd almost suspect an airleak in the exhaust system or possibly an intermittent ignition/sensor problem.

 

2006 Model Big Twins had a Service Bulletin M-1185.
This related to a driveability problem for what is generally known as a "cough". This may be what you are experiencing and describing as a backfire, which it is close to.

Anyway back then the fix, on Harley's dime was to replace your 8 degree injectors with 25 degree injectors and it fixed the problem. Look into the bulletin and see how to identify the injectors that you currently have. If you have the older ones then replace them.

 

Fuel filter?

 

ripsaw, your're dead-on about the sense of having a low battery every now and then. I felt the same thing, even though I always keep by bike on a trickle charger. I thought it was me, but you are right. I will keep my ear open to see if it also does it at the same time it backfires. And yes, it is a loud back fire, not merely a cough. I could tolerate a backfire on a 61 Volkswagen, but I don't think any reasonable running motor, especially one made this century, should be doing this. Over time, I think it can lead to problems.

 

I am sure the inner baffle when it gets rusty will eventual come out the back. Just order me a 2020 take off ebay and start again? HA It's in the exhaust pipe so no concern to me except the bang. I sure would not try to richen the idle to fix it since all that will do is reduce cylinder life. An FI cylinder will last twice as long as a carb cylinder. Bet that will wake this thread up

REMEMBER CGMARTIN IS TALKING ABOUT A LOW BACKFIRE POP AT THE START OF THE CRANKING OF THE MOTOR AND BEFORE IT STARTS. NINE TIMES IT WILL CRANK FOR SAY COUPLE THREE OR FOUR CRANKS AND START WITH IN THERE WILL BE ONE WITH A CRANK ONE CRANK OR SO AND POP LOUD AND CRANK TWO OR SO MORE AND START JUST LIKE THE OTHER 8

 

how do I get ahold of this service bulletin, or how do I found out if it was done already?

Thx

 

Ok. I've taken a look at my bike, and it still has the 8 degree injectors. it is a 2006 Heritage classic. other than the occassional back firing at start up, it runs fine. Would there be a major improvement in going to the 25 degree? Can it be done without the re-mapping? Any idea on cost?

 

Ask this specific backfire problem with hopeful better title in another thread.

https://www.hdforums.com/forum/gener...y-do-that.html

also some 8 ver 25 threads

https://www.hdforums.com/forum/touri...-question.html

https://www.hdforums.com/forum/elect...injectors.html

https://www.hdforums.com/forum/dyna-...injectors.html

https://www.hdforums.com/forum/dyna-...-my-06-wg.html

how to identify
http://www.mastertune.net/downloads/...isting-v37.pdf