Originally Posted by jimmers1817

Check out this article on the "popping" issue. FWIW, I think you'll find more decel popping posts here from riders with tuners than w/o. I have a stock bike same year as yours with 1.75s on it and have never had decel popping. Bike runs fine (and with sooty plugs)

Just saying don't be surprised if after putting a tuner on your bike you have the same problems. And worst gas mileage to boot. BTW, plugs can be cleaned and reused. Mine are typically covered with soot when i pull them which goes against all the talk of Harleys running too lean and also the usual reason cited for putting tuners on.

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 jut 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, Honda has 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 Honda! Of course, normally, that massive bazooka pipe Honda hangs 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”.






_____________________
2008 Heritage Classic: His
2008 Deluxe: Hers

Originally Posted by texaswiz

Common problem but not always real easy to diagnose over the internet. If all you have added were the 2" Rush slip ons, that is not the inherant problem. Your bike's on board computer and fuel injection system have enought latitude built into them to compensate for that. Look at your plugs. Sooty and black, it is running rich. Real white, too lean.

If you have added a new high performance air cleaner into the equastion as well, then you have opened up the air capacity a whole, whole bunch. The Harley Screaming Eagle air cleaner (Stage I) probably does more than anything else to improve increased performance. So when you add the slip ons + the new air cleaner you are in essence running more air and fuel through the system than before. Your bike can rejigger itself easily with just the slip on but when you now add the high capacity air cleaner into the mix, it will have to have some help. That is where the Stage 1 download you get from the dealer comes in. Amongst other things it increases the rev limit and changes the timing to effectively take advantage of the less restrictive mufflers and a new higher capacity air cleaner. There are some other things it does too but only God and the Harley Fuel Injection engineers know and neither is talking.
Now having said that, it is a rare occassion when I see anyone who replaces their stock mufflers with new slip ons that actually buys new muffler clamps. Consequently most bikes have some sort of deceleration popping or gurgling going on. When you are cruising along and take your hand off the throttle while the motor spins down, it wants to suck air into a leaking muffler connection unless the muffle clamps are on tight enough. It is just something about having to spend $10.00 for those damn muffler clamps that galls everyone enough to the point where unless they twist one off...they ain't gonna buy new ones. Most people do not use a torque wrench to tighten their muffler clamps, they use the tried and true "Armstrong" method. The Harley manual calls for 38-43 ft. lbs of torque on a muffler clamp. From personal experience I have noted that at about the 35 ft. lb range the clamp will seal perfectly, if it is in the right position. I don't know anybody including myself who can acurately do this without a torque wrench. In this case, close ain't good enough. Another thing I see often is that the muffler clamp is slid too far up the muffler itself. The mufflers have slits on them which allow the clamp to compress there and close up any gaps. Most I see are way beyond the slits in the mufflers and the muffler clamps don't do much good. Most people tighten up until they hit 60 or 70 ft. lbs and about then the clamp tears apart or the bolt breaks. If you don't own a cheap beam torque wrench, try to borrow one. As long as you don't over torque them you might get a second use out of the clamps if you are lucky, but don't count on it. Sometime you have got to bite the bullet and pony up that 10 bucks for a new clamp.

Originally Posted by harley_nova

Originally Posted by jimmers1817

Check out this article on the "popping" issue. FWIW, I think you'll find more decel popping posts here from riders with tuners than w/o. I have a stock bike same year as yours with 1.75s on it and have never had decel popping. Bike runs fine (and with sooty plugs)

Just saying don't be surprised if after putting a tuner on your bike you have the same problems. And worst gas mileage to boot. BTW, plugs can be cleaned and reused. Mine are typically covered with soot when i pull them which goes against all the talk of Harleys running too lean and also the usual reason cited for putting tuners on.

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 jut 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, Honda has 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 Honda! Of course, normally, that massive bazooka pipe Honda hangs 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”.






_____________________
2008 Heritage Classic: His
2008 Deluxe: Hers

Originally Posted by harley_nova

Well, I think I may have fixed the problem.
I pulled the spark plugs Monday and took a look at them and they were clean. Gave them a light sanding and put them back in.
I then took apart the exhaust clamps and put them back on and tightened them to the specified torgue that was mentioned in the manual. My GOD, there was no way that I could have tightened them much with 'Armstrong' strength!!
I guess I should have borred that torque wrench sooner. Would have saved myself the stress. It still pops a bit, but according to the article jimmers1817 posted, it is completely normal.
Thanks for everyones help.

Hey Rolly, I am not sure if you will be fine with your current download or not. They probably have different ones for slip ons and full exhuast. Definitely something to look into.

Originally Posted by jimmers1817

[...]

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

[...]

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

Yup. If you’ve jut 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.