Just bought a new to me 2001 FLHTCi, a true survivor with 30K miles in mint condition.

Stage one w Screaming Eagle pipes and Fuel Injected and she is backfiring when I let off the throttle decelerating. Nothing too bad and solved by adding a few RPM I was just wondering if this is normal?

Also wondering if this motor differs from my other Harley's which had counter balanced engines perhaps resulting in less backfiring?

 

Are you certain it's backfiring or is it just decel popping?

2010 Limited with some stuff

 

popping out the exhaust most likely caused by,exhaust leak,or improper tune.

 

What kind of device do you have to alter the mixture? If you have screaming eagle exhaust, that has the net effect of making your mixture leaner. Xied, Fuelpak PowerVision, and etc would be common brands. Check to see if you see something extra attached . . . perhaps a bypassed O2 sensor? If not, then you'll probably need to purchase something to enrich the mixture . . . Just a thought . . .

Mark!

 

Sounds like mine,2001 with 37k kms last year when I got it.Check under the covers for a PCIII,mine didn't do any decel popping until I started messing with it by changing mufflers,air cleaner and adding the PCIII,exhaust leak and or tune are likely causing your issue as well.

 

Copy and paste, but best explanation for Decel pop and tuning. Short story for the TLDR folks; a "properly" tuned bike will pop on decel with aftermarket pipes.

Burn Baby Burn

The last thing I want to address today is the subject of deceleration backfire, or “popping”. This topic generates a lot of concern from inexperienced riders, or even from experienced guys who just hate the noise, so lets take a look at what causes it. But first things first, lets define the issue:

Deceleration Backfire is caused by fuel burning in the exhaust manifold or header.

No ifs ands or buts, that’s what causes it. But the bigger question is how does gas get there in the first place, and that’s a bit more complicated. Generally, there are a variety of ways it gets there, and a variety of things that can make the backfiring worse. But there’s a kicker, and something you should understand before we go any farther:

A motor in perfect tune will exhibit deceleration backfiring.

Therefore, just because your motor is banging it up, doesn’t mean there’s anything wrong. And consequently:

Getting rid of the noise means de-tuning your motor.

Yup. If you’ve just got to eliminate that popping, you’ll have to accept the fact that your motor is going to be forced to run rich to do it, and that isn’t necessarily a good thing. So lets talk about what causes the problem.

Ok, so you’re riding along at some given rpm, and suddenly you decide to decelerate, and you reduce the amount of throttle. This causes an “overrun” – that is, the motors rpm is turning faster than the fuel provided can support, so the motor begins to spool down. This causes a couple of things to happen.

First, when you close the throttle, you are also closing the throttle plates. This reduces the air and fuel flowing into the motor, and increases the vacuum (lowers the pressure). This results in less air and fuel in the cylinder during the power stroke, which in turn results in a lower pressure in the combustion chamber. Remember I said earlier, that the A/F mix burns faster in proportion to the pressure applied? Well, when we reduce pressure this way, the mix burns slower. This results in two things happening.

1. The lower burning fuel generates less heat, and the cooling effect of the non-burning fuel tends to “quench” the flame front, or slow it down even further. Because the mix is burning much slower, the exhaust valve can open before all the fuel is consumed, and the unburnt fuel is ejected into the exhaust.
2. The engine designers, in order to promote smoother idling and better combustion, retard the spark when the throttle is shut, and this results in the mix being lit later.

So, now we end up with unburnt fuel in the exhaust, and burning fuel being ejected into the exhaust, and bang! Backfire. In addition, Manufacturers have added a device called a “programmed air injection valve” (Pair Valve) that actually injects some fresh air into the exhaust to help this process along – since fully burning the fuel results in cleaner exhaust. So the backfiring is not only a normal part of the engines operation, it’s also intentionally amplified by the manufacturer! Of course, normally, that massive bazooka pipe hanging on your bike hides most of the noise, but it’s there, even when you can’t hear it.

So the bottom line, is: That backfiring is perfectly normal and expected. If you’ve just got get rid of it, that’s up to you. You’re entitled to set your motor up the way you want, and your goals are your goals. But don’t refer to it as “fixing” the popping. Rather, the correct way to think of it is “de-tuning a bit to get rid of the popping”.

There are a few ways you can do this.

First, use the stock pipe. It will hide the sound, by absorbing it into mass, and masking it with the larger baffle space. Second, you can add more fuel during deceleration. This has the effect of raising the chamber pressure slightly, which burns a little more before the exhaust valve opens. Lastly, you can remove the Pair valve, which reduces the amount of available oxygen in the pipe to burn the unburnt fuel.

 

In addition to what everyone else has said here; Make sure that you are letting the throttle return completely. If it is left open just a bit sometimes you will get decel popping.

 

Great article, thanks for that. I definitely think the tune is right and there are no exhaust or intake leaks, re-mapped and running great. Like the article said I would have to de tune to eliminate the backfire. Adding a little fuel does eliminate the backfiring but I never realized why until now. (Raises the pressure and burns better.)

My softails had stage one and very little backfiring so I wondered if counter balancing makes the difference.

Spoke with two other owners of similar Electra Glides who confirmed this backfiring on deceleration is normal. I don,t know if newer models do it or not. I find it a little annoying but it beats stock pipes and running rich.

 

Yeppers, mine winds down like a small block V-8 when I leave the trottle completely closed, no decel pop at all..... but if I leave my hand resting on the grip, just cracking the throttle open ever so slightly, I can get decel too. (Make certain that your forward-most cable isn't too tight while you're at it.)