Exhaust Popping

[Mentok]

Hi there, excuse my ignorance of these things I did a search but couldnt find what I was after as Im not sure of the correct terminology to use.

I recently bought an 03 955 Tiger and took it for a good run a few days ago. I noticed upon rolling off the throttle that there was a fair bit of pop/backfire from the exhaust. Someone I spoke to mentioned this may mean something in the engine needs balancing. Is this so or is it just normal for the bike?

The tiger is only my second bike, the previous was a VFR with the VTEC nonsense on it and Im not very mechanically minded.

Any help much appreciated. The bike is due to go in to the workshop this week as it has a leak from under the right side of the tank (fuel?). It would be great if I had an idea of what the problem if any is so I dont get ripped off.

Thanks again  :)

[ChazzyB]

Popping and banging? They all do that, Sir.

[Mentok]

Thank you kindly meister :D

[Spud]

Popping on the over run makes me laugh  :twisted:   cheers Spud  

[NKL]

mine doesn't

[jphish]

My 06' Tiger 'gurgles & rumbles" a slight bit on decelleration - but nothing even close to  "backfiring"!!  I've got the TOR exhaust & ECU remap - perhaps thats the difference? A bit richer mixture ?

[HockleyBoy]

Popping and banging? They all do that, Sir.

+1

And I love the sound  :D

[Danny955i]

There's a group of us on here:

MetalGuru
BixxerBob

and a few others, who are slowly decoding the 955i's pop/gurgle phenom.

99.9% of Tigers do it... stock or not.

We've been editing maps, and settings for the 955i trying to find the best balance of economy, power, and reduce popping.

Seems to be a common theme that adjusting Long-Term Fuel Trim, is a big help, as well as loading in the newest maps provided by TuneECU/Triumph and tweaking from there.

Just know that NOTHING IS WRONG WITH YOUR BIKE... they're just a lumbering, chunky, beast of a runner! :)

[Danny955i]

Also...

How many miles are on your bike? If you're around 16-20k, you should get the valves checked and the throttle-bodies balanced...

About a 400-500 dollar job at any dealership, but it's a fairly universal process... so your local motorcycle shop could probably pull it off for less than 300.

Good luck!

[topher0268]

It's generally referred to as "popping on deceleration". It's a common occurance and it doesn't mean there's anything wrong. I found this on another forum hope it helps explain what you're hearing:


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".
 
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.

[aesdj]

Sorry guys I don't get this bit:-

"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."

Now I'm running a race can with one of the 2 removable baffle out and the latest offroad tune so by rights my bike should be running almost exactly the same except for the exhaust make to everyone else but mine doesn't pop & bang. I thought that one of the causes that makes the bang louder as all bikes bang, its just it may just come across as a burbble instead of the bang is the pipe sucking in air at any of the joints. Now when I fitted my can I used exhaust paste and thats was why mine doesn't bang loud.

Right now for the next bit that proves my thinking:-

"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 (made louder) by Honda!"

So Honda suck air into the exhaust to amplify the bang to burn the un-burnt fuel to get the exhaust to run cleaner, which is the same as not having a proper sealed exhaust not by tuning the bike to run rich as said above. Sorry for the long reply but I thought I'd clear that up.

[aesdj]

Sorry forgot to write this bit

SO IF YOU WANT TO MAKE THE BANG QUIETER SEAL THE EXHAUST PROPERLY.

[Danny955i]

I wish there were a picture to describe this action...

1 of 2 things happens on overrun.

Backfire and Popping.

Backfire is when fuel gets pushed through the combustion chamber unburnt and ends up in your exhaust pipe, then when a hot blast of exhaust flows through on the next stroke it ignites the fuel in the exhaust and boom. Backfire.

Popping is when cold air and hot air collide within the exhaust. This can happen one of two ways.

1. On over-run, whether your throttle is 100% closed or not, air is getting into your motor... So if you're coming down from say 6000rpm, that hot motor is going to pull some cold air into it. Adding more fuel (say upping your main jet or Long Term Fuel Trim) will combat this by simply giving the motor something to burn rather than just pumping the lean cold air through the hot system.

Think of it like thunder... High pressure meets low pressure... rumble.

2. On over-run, or even normal riding, if you have a hole in your exhaust... this could be a crack, a weep-hole in the base of your exhaust can, or a bad seal on a slip on system... this will also introduce cold air into the system. When on over-run, less exhaust comes out of the tail pipe, since the motor is revving faster than the fuel intake the exhaust can have a slightly lower pressure than the intake... thus it can suck in some cold air from the outside through one of these small holes. Thus leading to the above explanation of high/low pressure.

-----

What I've come to realize is. Tune your bike so it performs to your liking... as long as you're not going to detonate your combustion chamber, or fry pistons from running to lean, then you're OK.

Slightly rich is good for every day... slightly lean is good for more power.

Popping will happen no matter what.

[Mentok]

Thanks for all the replies and putting my mind at rest guys. I don't mind the sound at all I was just concerned it may have been a fault.

My bike has around 22000 miles. Despite promises that the bike had been well checked and serviced etc by the garage I bought it from it is becoming clear this is not the case (fuel leaks, corroded brake callipers etc) so I was concerned this may have been a bad engine problem.

Again thanks for all the advice!

 :D