Backfire

I have an 05 Road King Custom Fuel Injected that I have just installed the following:
Arlen Ness Big Sucker Stage 1 kit; Vance & Hines Oval Slip - ons, Rev Tech DFO.
After installing this items and adjusting the DFO I am getting backfire on downshifting or if I release the throttle while still in gear. I have tweaked the DFO based on a call to Dobek but still am experiencing the problem. My current DFO pot settings are #1 = 4 , #2 = 6, # 3 = 4, # 4 = 4
My question what would be the causes for the backfire in this situation? Is it a lean or a rich fuel mixture or something different that still needs to be tweaked with the DFO?

Thanks

Look over the add on mufflers as well as your header pipes for air leaks. Dutch

Like Dutch suggests, ..... air leaks, or running lean will usually give you the popping when a quick decel happens.

Exhaust Popping

Have a 04 road king custom with identical set up except I have a power commander. Took it to the Harley dealer and seems ok to pop however I suspect its running slighty lean.

Exhaust popping 2

Have just spoken to a Harley tech, say that the result of popping could be because of a leak and the cold air enters the exhaust mixing with the hot air causes a popping sound.

Alternatively because you decelerate from high RPM the engine requires high air demand and reverse flow occurs in the exhaust causing this phenomenon.

On carbutretted engines you can richen the mixture, but on fuel injected models with electronic chip the fuel /air mixture must be adjusted on the module. This is because as you close the throttle on a fuel injected bike the mixture leans off.

Hope this helps

I have a 04 RK Custom with similar setup. I don’t remember what my DFO setting are but it is what ever the recommended setup was. I think it is the first one in the 2-3 position and everything else on 0. the hesitation that I had when stock went away and with the new air cleaner and pipes I had no popping and strong acceleration so I didn’t bother making any adjustments. Start over at the recommended stock settings and go from there. Good luck. Johnny O.

This happens a lot when the pipes are replaced.
When you replaced the pipes you modified the REverb or back preassure into the cylenders .
On a internal combustion engine back preassure is used to mix the fuel air mixture in the head to get a more complete combustion and more HP.
The popping you now hear(I think it's totally cool) is unburned gasses igniting in the new hot pipes. Tuning the pop out is usually VERY difficult.
In the shovel days we could kill the ignition and the turn it back on to get a nice flame out the back from the unburned fuel mix.
I know this don't solve your problem but I hope it gives you some insite as to what's happening.

Slayer the same thing

will happen on a 5 1/2 straight axle duelie....in the service we'd get 'em going good (especially down hill) then let off gas, pop pop pop!!!shut them off pump the pedal for extra fun and blam big ol' explosion!! actually the muffler blew out!!! a few times Try explaining that to the fellas in the motor pool when returning the vehicle....Hmmmm must have been..I don't know..after the third time of replacing the mufflers on the trucks I did come up with Hmmm..must have been a bad batch of Mufflers.... Did it on the older bikes too...bet the counter balance 88bs would destroy themselves since the counterweights are in the mix. seen a couple get damaged on dynos and those drag racing machines where they strap the bike down...they get up there in RPMs then let up and slam the counter balances/oil pressure drop (so to speak) kinda off subject but hey just ramblin on a bit...Good luck on yer tuning in Big BIKE..... ps I got an 88a Hmmmm...I wonder..... just for old time sake maybe once I'll do a blammo in a tunnel for fun!!!

I know this is an old subject post but for anybody reading it....... Even with the all stock setup that was on mt 05 RK there was plenty of decell popping. You have to listen hard because of the stock quiet mufflers but, all that decell popping is in there.

On my '04 RK, I have V&H Ovals, Ness Big Sucker, and a Power Commander. I initially hard a lot of popping on decel. Call Dynojet. They modified my map by enriching 0 throttle setting and popping went away. I also replaced the clamps that came with the Ovals with the Harley clamps. They make a better seal with the head pipes. Hope this helps some.