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Andy VH
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   Posted 4/21/2008 1:51 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Well actually, it is NOT really backfiring. We get a lot of posts here like "my bike is backfiring, what can I do about it?" So maybe this sticky will help clear some thngs up. Backfiring, is actually fairly rare these days because of electronic ignitions and the high reliablilty of engines, and the lack of things we can actually mess up on an engine. Real backfiring means the engine is out of proper timing and the fuel/air mix is getting a spark and ignition at the wrong time, when the intake valve is open. Real backfiring is actually the bike "spitting up" in a sense, backwards through the carb or intake.
 
So, the popping you are hearing is not back-firing. It is a popping resonating sound generated by a lean condition on decel. When you suddenly close the throttle, the incoming air is choked off and the closed throttle also causes the bike to return to idle on the very lean idle circuit of the carb(s). However, momentum of the bike is actually "driving" the engine in a sense, and that engine is still spinning at rpm that needs far more gas than the closed throttle/carb can provide. The engine is still spinning but the incoming fuel rate is very low, until just enough builds up in the combustion chamber to "fire" on the exhaust stroke of the engine.

To know this for sure, the next time it happens, pull in the clutch and the popping will stop immediately, because the bike's momentum is not pushing the engine to spin. Don't "change the plugs" like some people suggest, its a waste of time and money. Messing with the ignition timing really won't help either, because it is still a lean fuel/air mix on decel that is the cause. Note, I said cause and not problem, because the popping is not at all damaging to the bike. So don't expect your dealer to fix the "problem" under warranty because it is not a warrantable situation. The EPA drove this more than anything else. 
 
A recent update on this. Ever wonder why the stock mufflers on your bike are so big and heavy? Well, one reason is sound attenuation. Big mufflers provide a lot of volume for the rumbles and popping in the exhaust to be toned down by resonating in the larger muffler canister. Motorcycle builders also have to meet sound regulations along with emission standards. Some of that sound proofing is in the mufflers. But aftermarket mufflers, easier breathing, usually lighter and smaller, don't offer that same volume. Less volume, less sound attenuation = more noise and more popping. Again, don't complain to the dealer about this unless you plan to spend the money to correct the fuel/air mix ratio to make up for the increased airflow through the engine.

Modifying the exhaust (especially if it gets louder) will only make it worse, and louder when it pops. Because most aftermarket pipes produce "lower back pressure", it makes matters worse yet because lower back pressure pipes actually cause the fuel/air mix to LEAN OUT EVEN MORE. The solution is in the carbs, and it requires a richer fuel/air mixture. The only logical way to do that is spend about $300 to get a Dynojet or K&N brand "jet kit" installed. Do not mess with that carb jets yourself, do not mess with airbox, do not simply install a high flow air filter (which also can lean out the mixture) itself. If you want the bike to run a lot better and no pop on decel, spend the bucks on a jet-kit, you will be very happy with the results and it'll do a LOT more for performance than louder pipes ever will. In fact, I'd be willing to bet a jet-kitted bike with stock pipes would probably beat a stock carbed bike with aftermarket pipes.


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Post Edited (Andy VH) : 10/11/2011 4:07:34 PM GMT

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seth12
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   Posted 5/15/2008 6:17 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
yea but how else can u retime it? cuz i have a bike with a kick starter how would u fix this problem with one of thoes?
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Pale Rider
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   Posted 8/28/2008 11:40 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
A backfire that you hear in your tail pipe is actually unburnt fuel igniting in the pipe caused by an exhaust gasket leak somewhere allowing in enough air to accomdate igintion set off by the heat of the exhaust pipe, most of the time by your exhaust port. A backfire back out through your intake is most likely caused by a fuel, air mixture that is off, mainly lean, and can be corrected with proper jetting. Many times people will alter the exhaust with a high flow muffler or exhaust, but not change their intake. Or they'll install some sort of high flow intake and not change their exhaust. This creates an imbalance that will cause all kinds of performance and tuning problems, and very frequently accompanied by back firing through the intake on carburatored engines.

I am a retired Harley Davidson Technician. I've dealt with these conditions for years on end.

Post Edited (Pale Rider) : 8/28/2008 6:45:31 PM GMT

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Ada Ada
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   Posted 9/16/2008 2:11 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Pale RIder is using the phrase 'backfiring'. Does he mean 'backfiring' or 'popping'? I probably have a minor exhaust leak where the muffler goes onto the header pipe. Am I getting backfiring or popping? I probably have a lean tuned fuel injection. So, what's the fix?
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SoCalGirl
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   Posted 10/4/2008 9:54 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
This is a great explanation. My bike does the same when I close the throttle while slowing. I was going to talk to the dealer about that. My guess they would just tell me not to worry, this is normal ... without giving the explanation why. So your explanation has resolved that question in my mind.

Does this cause any harm to the engine?
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car5car
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   Posted 7/31/2009 8:33 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
I plugged rid valves on my 87 Vulcan 1500, popping sound disappeared. I don't know if that kind of valves exist on different bikes but if I see it on some another bike I will plug them too. Popping in exhaust should be called "front firing" :)
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alwayslearnin
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   Posted 10/28/2009 7:47 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
I was logging on to ask a question about "backfiring", and your explaination doesn't seem to fit my problem. I have a 2004 V Star 650 Silverado, engine stock-unmodified, with only 2100 miles (I'm the third owner, have only had it a little over a year) and the 'backfiring', actually a short sharp 'crack' or two when I roll off the throttle, just started...it wasn't there a week ago. It happens even if I am sitting still with the clutch in and just gun the engine, so it doesn't sound like 'real backfiring'. It only started after I filled the tank last week. When accelerating, it doesn't feel right, kind of sluggish and the throttle isn't normal responsive. Also, when I stop, the engine wants to stall, it has even stalled a few times, and this is after I have ridden about 5 miles, so it is warmed up. I talked to a service technition and he said it could be water in the 'float bowl', causing the mixture to be super lean, and it would have to be cleaned out. I have never owned a motorcycle before, so I am still learning what is 'normal' and am not yet mechanically familiar with the 'guts' of the thing, so messing with the bowl or carborator could be a disaster. If it is water, is there an additive to clean it out, or can the tank be drained and new gas added to solve the problem? Any other solutions?
Any help would be greatly appreciated.
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Andy VH
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   Posted 10/30/2009 7:03 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
You could try running some HEET fuel additive or Techron fuel cleaner in the next tank of gas. You might need to consider how your riding habits and frequency of riding, along with the gas you usually use, affects this. If the fuel you are using contains ethanol, the water in the ethanol may be building up in the fuel system. Plus, ethanol attracts water, and since the fuel tank on a motorcycle is vented to the air, it can suck in moistures that is in the air.

Next, what type of riding do you mostly do? Around town? Short rides? Lots of stop and go trips? That type of riding tends to cause more water condensation in the engine and fuel.

Also, how frequent do you ride? Every day, once a week, a few times a month? The more time the bike sits unused the more likely water can build up in the fuel system. Try some HEET, avoid fuel with ethanol, try higher grades of Shell or BP gas, and see if it improves. If it doesn't, then a trip to the dealer for sevice might be needed if you are not comfortable with wrenching on the bike yourself.


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alwayslearnin
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   Posted 10/30/2009 7:10 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
thanks for the advice. I don't ride a lot, usually once a week, and most of it is under 35mph. Bike is garage kept. I use Shell regular gas, don't know the ehanol content. I'll get some HEET and see if that helps.

I read somewhere here that Sea Foam is a good additive that can be added to each tank of gas. Is that a good idea? Will it help in the future?
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bsa_bob
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   Posted 7/11/2010 4:15 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
My 03 shadow popped and spit on decel.........i jus popped out the factory caps and used a screw driver.....set the carbs up a tad richer,wala, all the popping is gone!So next ..the triumph America is getting it done.....by me. Not hard to do on the shadow but working from the bottom of the carb[adj] on the America will be a bummer i think my two cents bob s
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alwayslearnin
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   Posted 7/12/2010 9:34 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
thanks. i drained the gas tank and filled it with new gas with sea foam and ran the engine for about 10 minutes. it started off rough, but evened out and now is fine. it must have been contaminated gas, so i am making a habit of adding sea foam to the gas each time i fill the tank since the bike might sit for a few weeks between rides.
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Andy VH
Where is the earth shattering kaboom!?



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   Posted 7/16/2010 6:35 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
Could also a a factor of where you live. In areas with higher humidity, or near the oceans, the extra moisture in the air does get into the engine and in the fuel tank through the vented gas cap. Up here in Wisconsin, fuel breakdown and degradation is not as much a problem in the hotter, southern states. In areas where gas evaporates more quickly, gas breakdown is much more of an issue if your bike sits unridden for days at a time.

So riding it more is one way to avoid gas going bad. Or add treatments to the fuel, because the newer gas formulations with added ethanol also make it worse for gas breakdown.


Training, the best safety and performance "equipment" you can get!
Get MSF trained, check out: http://www.msf-usa.org
 

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cadpunk58
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   Posted 2/20/2011 6:22 AM (GMT -7)    Quote This PostAlert An Admin About This Post.

I recently changed out the stock exhaust system on my 2008 Yamaha Road Star Silverado, (which is fuel injected) to the Cobra Drag pipes, and now have excesssive popping, backfiring, whatever you want to call it, while shifting up or down, before changing to the drag pipes, instead of changing the entire system, I was told that if I just replaced the stock mufflers with some slip-ons, I would achieve my goal, (which was better sound) but after installing the slip-ons, I noticed the cracking and popping while shifting, local biker shop told me that I would need a Power Commander to correct problem, and not to ride the bike until I get one, otherwise I would fry my exhaust valves, I was told by the local Yamaha dealer that if I replaced the entire system, pipes and mufflers, etc... that I would not need the power commander, and the popping and cracking would stop.... nono  well do your own research people.....most of the people you talk to, dont have a clue of what they are are talking about, even the dealers, they are there just to make a buck. There are so many different conflicting stories and messages out there, it is enough to drive you insane...roll

 

If by chance there is someone out there...who has actually worked on "fuel injected" models with this sort of issue, please contact me, I would really love to find the solution to this, before I have to take out a second mortgage to buy all the items that everyone else says I need...

Particulars:

Live in Riverview, Florida (so yes very humid), I try not to ride in the rain, mostly interstate travel (3-4 days /wk), the bike is garage kept, only has 6000 mles

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Easy Rider 2
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   Posted 2/20/2011 8:26 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
cadpunk58 said...

If by chance there is someone out there...who has actually worked on "fuel injected" models with this sort of issue, please contact me, I would really love to find the solution to this, before I have to take out a second mortgage to buy all the items that everyone else says I need...

Hopefully someone here can point you to a forum for your model bike; I don't know if there are any others here.
 
In general, however, you probably made too drastic a change in the pipes......or disconnected a critical sensor in the process.
 
How's the sound ??  Is it obnoxiously loud enough for you ??
If that's your objective, you may indeed have to get an aftermarket controller.
Or you could just enjoy the extra added noises. smilewinkgrin
 
I really doubt that you are in any real danger of burning a valve......but I don't know that for sure.
A plug check should indicate whether or not it's running too lean at speed.
 
 
 


 
 

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cadpunk58
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   Posted 2/20/2011 8:48 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
Easy Rider 2:
 
Well the sound is fantastic, if I could just get rid of the popping and cracking, like I was going thru the neighborhood shooting people or something...but anyway as far as having a sensor or electronic component disconnected.. the only items that were disconnected during installation were the O2 sensors, and both have been re-connected, I tried blocking off a portion of the air inlet (as I was told I could try from the dealer) on the air cleaner assembly...but unfortunately that didn't work either...so looks like I am heading to the parts house to get a PC.
 
thanks for the info
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Easy Rider 2
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   Posted 2/20/2011 12:01 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
cadpunk58 said...
 the only items that were disconnected during installation were the O2 sensors, and both have been re-connected,
But are they still mounted in the original locations ??
Even if they are, the different backpressure and flow in the pipes might be causing them to send different "signals" now.
 
Do you have a stock air filter in place ??
Inlet mods often have a larger impact than pipes do.
 
With advice like "partially block your air inlet", I wouldn't trust that dealer to work on a bicycle.
Having said that, however, you might be time and money and frustration ahead if you can find another shop that actually knows what they are doing to check it out for you before you take a "blind shotgun" approach to the problem.
 
Sometimes an exhaust leak up near the headers can cause the condition you describe........although drag pipes have about the same effect.
If you can find a simple and cheap baffle for your new pipes, that might solve your problem too........although it might reduce the sound you like so much.
 
I have yet to see a bike with unbaffled drag pipes/short shots that I didn't find obnoxious and WAY over the legal limits.
AND you need to be concerned about your hearing too.  Seriously.
 
YMMV.  How MUCH are you willing to spend to keep making a statement with your noise ??
 
 


 
 

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cadpunk58
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   Posted 2/20/2011 7:11 PM (GMT -7)    Quote This PostAlert An Admin About This Post.

Easy Rider 2...I understand what you are saying, and no I dont trust the dealer all that well, but I am very limited to where I can take the bike for service, in my area.

As for the location of the O2 sensors! they are not in the identical physical location as they were on the stock pipes, but within a few inches, the back pipe sensor had to have an extension for the connector which was provided with the new pipes.

I have checked for exhaust leaks at the cylinders where the pipes connect, and all seems good, the new pipes have baffles in them, and the sound is not that bad, granted it is much louder, but deeper sounding than the stock, but that is what I was looking for anyway, and believe me I have much, much louder pipes on bikes than what I have now, so breaking the legal sound barrier wont be an issue.

I plan to visit the bike shop tomorrow, and purchase the Power Commander, and get this thing tuned like it should be, if this dont work, I still have my stock pipes and mufflers in my garage, that can be re-installed with no problem. I will just have to live with it the way it is, if I can't get these Cobra pipes to work.

 

but thanks for the help and advice, I appreciate it very much!! smile  Ride on...and be safe!!

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ukbball
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   Posted 3/7/2011 5:05 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
I just bought a 2005 honda vtx1300 and on the way home it ran fine until i decelerated coming to a stop and the bike would just die when i got around 30-40mph, it probably died on me 7-8 times.

I figure it is just dewinterizing itself or whatever and its also been sitting for 2 weeks solid before this ride and im sure he didnt ride it this winter. I had an hour drive home on it and it seemed to get a little better when i got into my home town but it still died on me when i pulled in the driveway of my house after riding it for an hour straight. Is this something to be concerned about or just a minor issue or will it work itself out? Ive never owned a motorcycle before so i am clueless thanks.
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Easy Rider 2
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   Posted 3/7/2011 6:09 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
ukbball said...
I just bought a 2005 honda vtx1300 and on the way home it ran fine until i decelerated coming to a stop and the bike would just die when i got around 30-40mph, it probably died on me 7-8 times.
Welcome to the forum.  Sorry you're having trouble.
It's usually best to start your OWN thread rather than jumping in on someone else's problems.
 
Have there been any changes made to the stock pipes or air filter input ??
If so, I'd be tempted to take it back and demand your money back.......or insist that the seller get it fixed.
 
Might respond to a healthy dose of carb cleaner and a little increase in the idle setting.
Could be a loose battery cable too.  Could be lots of things.
 
A dealer visit is probably in order.


 
 

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ukbball
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   Posted 3/7/2011 9:27 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
K thanks for the info easy I also meant to say that it will stay running if i nurse the throttle and when it does die and i restart it i have to give it a lot of gas just to start.

I actually bought it from a big time dealer, they said they got it in on trade couple weeks before (i bought it from a Harley store) im sure they didnt do anything to the bike because they said when they get trade ins from a different bike they ship them put and wholesale them so im sure they didnt put the vance and hines pipe on there. A guy from the store had to go get it from their warehouse and rode it to the main store he come out and told me it ran fine thanks easy rider
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Easy Rider 2
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   Posted 3/8/2011 8:27 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
ukbball said...
 and wholesale them 
 
 A guy from the store had to go get it from their warehouse and rode it to the main store he come out and told me it ran fine
Did you compare the price you paid to Kelly or Nada, etc.
I'll bet you didn't pay "wholesale".
I also bet that they told you TWO lies.  shocked
 
I hope you learned to NEVER AGAIN buy a used bike without an extensive test ride.......especially from someone who claims they have no responsibility for what shape it's in.
 
Good luck; I hope a little carb cleaner fixes you up.......but somehow I doubt it.
I really think you are going to have to find a dealer and pay them to go over it.
 
What are you doing with the choke ??  Leaving it on more and longer might help too.
 
 
 


 
 

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DavidFernandes
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   Posted 4/20/2011 1:37 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
Backfiring was more common in the 2 stroke early engines and the electronic timing solved that problem but it still happens some times on certain bikes. when the engine is revved and the fuel is shut off too quickly with the engine rpm still high the only gas the engine gets is mostly air and this explodes and a different compression and timing which is back-firing.
cool

Post Edited By Moderator (Rich_S) : 4/20/2011 4:15:34 PM GMT

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David415
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   Posted 7/12/2011 12:57 PM (GMT -7)    Quote This PostAlert An Admin About This Post.

Its has to do with the emission control on the bike or too lean pilot circuit.

There is a fix for the problem.I have a vtx 1300 R 2006 with the same problem.Vance and hines big shots and rejeted the carb.

too a .200 jet. Need to modify the emission control on the bike with reed blocking plates.or plug the reed ports on the engine.

http://www.vtx-parts.com/honda-vtx-fury-1300-1800-pair-valve-cover.html

This is the basic design for the vtx 1300 R .You can do this with bikes that you cannot get the kit for.

Caution you will have to remove the emission control valves and block the reed ports to the motor by plugs.

For more info please contect with this site.The kit does fit a vtx 1300 r honda.turn

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Andy VH
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   Posted Yesterday 8:42 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
Some of this taken from an earlier response is right, but not all of it, "Backfiring was more common in the 2 stroke early engines and the electronic timing solved that problem but it still happens some times on certain bikes. when the engine is revved and the fuel is shut off too quickly with the engine rpm still high the only gas the engine gets is mostly air and this explodes and a different compression and timing which is back-firing."

Different compression and timing which is back-firing? Compression? Nope. Timing? Nope. Back-firing? Certainly not!

The compression is a set condition determined by the engine design. It does not change other than over time carbon builds up on the piston top and slightly raises the compression. But it does not change by revving the engine and quickly shutting the throttle. The only other factors that change compression are cylinder/ring wear, improper valve clearance setting (too tight), or maybe oil seepage past the valve stem guides.

Timing does not change with modern electronic ignition systems, unless there is a mechanical fault in the engine, like a very worn cam chain tensioner, and even that is not likely. Maybe a bad cam or crank position sensor, but those either work or fail, no in between. Old point ignition systems would wear and get out of timing which could cause the spark to occur when an intake valve is still slightly open, which then would cause a real back-fire out the intake, not out the exhaust.

Again, REAL back-firing is a backwards pressure wave out the INTAKE side of the engine. Anything such as exhaust popping out the EXHAUST cannot be termed back-firing because it still follows the natural exhaust flow out the engine. Even in the case of quickly revving the engine and shutting the throttle is still EXHAUST POPPING because the momentum of the engine crankshaft and flywheel/clutch basket is causing the engine to try in suck in more air against a closed throttle.


Training, the best safety and performance "equipment" you can get!
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Andy VH
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   Posted 10/11/2011 9:06 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
In response to the comment about to do with a bike that is fuel injected, I can say this.

My BMW R1100RS is fuel injected, and being a twin cylinder bike the pistons are fairly big, like many big twin engines from all the major builders. Also, my bike has a large canister stock muffler, which is intentional to dampen out the popping caused by the closed throttle lean conditions commonly cause by modern fuel systems and emission regulations.

When the muffler failed and cracked at the outlet, I thought "lets see what's inside." I cut the canister off, studied it and then designed/fabbed my own baffle system to allow easier flow and a bit more sound without being noisy. I had it TIG welded back together and I got more sound without being noisy (no one has ever even commented it is load at all). But, the exhaust popping on decel was significantly more noticeable, because the easier flowing exhaust actually leaned out the fuel/air mix.

So on my bike I installed a Techlusion kit which allowed me to dial in the fuel/air mix I needed for four differrent throttle/rpm conditions. I was able to "tune out" the popping on decel to a level I barely even notice anymore. So for fuel injected bikes you'd have to install some form of "chip", or Power Commander, or Techlusion device to compensate for the exhaust.


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