Backfiring like crazy

[RuoskaNZ]

Only really noticed how major it is today after a few hours riding today but with heavy throttle usage e.g. a quick trip over the Rimutakas,
it pops away quite a bit when you let off.
I may be using the wrong terminology as when car backfires you can hear it a block away.
Am pretty sure this is abnormal whatever it is.
Is it bad for the bike at all?
And what would be causing it?

Bike is a GSX-R600 K9

Help appreciated.
inb4 "dont let off"

[Nova.]

dnt let off

[mossy1200]

Mine does that. I have practised controlling it with throttle control so it does it louder when passing girls walking along the street.:clap:

[skippa1]

excessive decel popping or backfire is most likely an exhaust leak

[RuoskaNZ]

dnt let off:ar15:


Mine does that. I have practised controlling it with throttle control so it does it louder when passing girls walking along the street.:clap:
You would have to be going pretty hard around town to replicate the event.

excessive decel popping or backfire is most likely an exhaust leak
I have an aftermarket exhaust system, would there be a problem with that that is causing it?

[Road kill]

:ar15:


You would have to be going pretty hard around town to replicate the event.

I have an aftermarket exhaust system, would there be a problem with that that is causing it?

How long has the exhaust been on and did you have it tuned for it ?

[RuoskaNZ]

How long has the exhaust been on and did you have it tuned for it ?

I am unsure, I bought the bike as is.
Is there any way to tell if it has been done?

[Brayden]

I'm no expert but if you accelerate heavily then when you let off the backfire will be unburnt petrol because you've been giving it heaps of gas I don't think it's bad.

Also the 'popping' noise sounds bad ass I don't know why your complaining x D When you put an aftermarket exhaust on you need to the bike as it will run differently

[RuoskaNZ]

I'm no expert but if you accelerate heavily then when you let off the backfire will be unburnt petrol because you've been giving it heaps of gas I don't think it's bad.

Also the 'popping' noise sounds bad ass I don't know why your complaining x D When you put an aftermarket exhaust on you need to the bike as it will run differently

I know the general principle behind a backfire, but something causes it to happen.
It is just a little off putting really, and am worried I am doing damage to it somehow as a cause or product.
Probably a stupid worry but meh.

[Fast Eddie]

a backfire is usually like one big bang though after some rough running..

if your just getting a few baffles and muted rumblings its prob just from high revs, bits of unburnt fuel and high exhaust temps or the air rushing past the muffler or something - just having fun. race bike sounds like that all the time during decel/letting off the throttle

[DrunkenMistake]

Mine does that. I have practised controlling it with throttle control so it does it louder when passing girls walking along the street.:clap:


Hahaha im glad im not the only one,
I try time it through the main drag so just as you go past the main entrance to the mall, it echos through a bit wanky, but fin all the same

[bogan]

Technically it is an afterfire, backfires come back through the intake. Generally caused by it leaning out, then not getting ignited as it passes through the cylinder, but igniting when it hits the exhaust and contacts the flame from gas that has been ignited.

My bike is carb'd and has ACVs, air cutoff valves, which richen it up when under heavy engine braking. EFI bikes should detect the same condition, and inject more fuel.

[SMOKEU]

Being EFI the computer should sort out the fuelling for the exhaust mod.

[Berries]

It is just a little off putting really, and am worried I am doing damage to it somehow as a cause or product.
Probably a stupid worry but meh.
Mine is backfiring like a bastard now. Downhill, off the throttle, it is terrible. Looking at the corrosion on the eight year old OE downpipes and the superficial cracks in the mufflers I suspect an exhaust leak somewhere. Can't be arsed finding it though.

[bogan]

Being EFI the computer should sort out the fuelling for the exhaust mod.

I think you'll find even if it has an oxy sensor, it can only make minor adjustments, primarily there to increase the fuel efficiency across altitude/heat/humidity changes. Haven't heard of any that will successfully adjust for an aftermarket exhausts.

[darkwolf]

When was the last time the bike was tuned? I'm assuming it will have multiple carbs (4?). It may be that they are outta balance and over/underfueling on overrun. I had it with my VTR until I had the carbs balanced. Seems my fuel mix was also out. The hotter the bike got the more likely it was to occur.

[RuoskaNZ]

So, a hole/gap in the pipe somewhere.
Or a problem with the ECU not being able to allow for the AM exhaust?

Wont be a problem with the carbs as it is EFI.

Will try and get in touch with the previous owner to see what he did to it I guess, and get him to explain these random wires lol.

[ducatilover]

Is this a problem only after very long rides?
Or is it doing it all the time now?

You should be able to hear an exhaust leak.

[RuoskaNZ]

Is this a problem only after very long rides?
Or is it doing it all the time now?

You should be able to hear an exhaust leak.

It only does it when everything is well warmed up, and under heavy throttle usage.
Such as passing cars in short spaces, or racey corners e.g. Rimutaka hill.
It pops and rumbles for a bit when you let off.
The other bikes dont tend to do it, maybe I just cant hear them.

[ducatilover]

If it's not major popping I wouldn't get too fussed.
May be worth pulling the plugs and checking if they're in the correct heat range.

[skippa1]

EFI wont make up for an exhaust leak and I think only BMWs run 02 sensors that have anything like an extensive range they sense in, most are short range and only give an indication of the exhaust being in or out of spec to the ECU. In other words "im lean give me more fuel" or "im rich, cut fuel". You wont necessarily hear an exhaust leak, the most likely culprit is the gasket between the head and manifold, it only has to leak a smidge to cause the popping.
Of course you may find that it is a natural product of the after market exhaust you have and you cant tune it out. A lot of bikes dont even have a method of tuning the ECU and fuel injection to that degree. Is it really that bad or are you compaing your bike with others? That may be like comparing an apple with an orange and saying they ae the same because they are fruit:eek5:

[GrayWolf]

Only really noticed how major it is today after a few hours riding today but with heavy throttle usage e.g. a quick trip over the Rimutakas,
it pops away quite a bit when you let off.
I may be using the wrong terminology as when car backfires you can hear it a block away.
Am pretty sure this is abnormal whatever it is.
Is it bad for the bike at all?
And what would be causing it?

Bike is a GSX-R600 K9

Help appreciated.
inb4 "dont let off"
As already suggested, if exhaust is aftermarket? Either a small leak somewhere, or unburnt fuel igniting in the system.... The old brit bikes used to do it a lot when fitted with Dunstall megaphones..... As long as the mixture (jets/or injector setings) are correct for the system? Just enjoy,,, like Mossy (same bike), mine has a level of 'popping' on overrun 'built in' by the factory.


Being EFI the computer should sort out the fuelling for the exhaust mod.


I think you'll find even if it has an oxy sensor, it can only make minor adjustments, primarily there to increase the fuel efficiency across altitude/heat/humidity changes. Haven't heard of any that will successfully adjust for an aftermarket exhausts.


Supposedly the new Power Commander V with an O2 'optimiser' does alter the settings by tricking the reading (false info) going into the ECU, the MT has a closed loop O2 system to 2.5k rpm... and it is being used to overcome that when running a standard/stage 1 bike... retains standard ECU

[ducatilover]

EFI wont make up for an exhaust leak and I think only BMWs run 02 sensors that have anything like an extensive range they sense in, most are short range and only give an indication of the exhaust being in or out of spec to the ECU. In other words "im lean give me more fuel" or "im rich, cut fuel". You wont necessarily hear an exhaust leak, the most likely culprit is the gasket between the head and manifold, it only has to leak a smidge to cause the popping.
Of course you may find that it is a natural product of the after market exhaust you have and you cant tune it out. A lot of bikes dont even have a method of tuning the ECU and fuel injection to that degree. Is it really that bad or are you compaing your bike with others? That may be like comparing an apple with an orange and saying they ae the same because they are fruit:eek5:
I think you're right, I haven't yet seen a factory fitted wide-band 02 sensor on a Jap bike.

Just enjoy,,, like Mossy (same bike), mine has a level of 'popping' on overrun 'built in' by the factory.




I like it when they do this, nothing like a good sounding engine popping and snorting on the over run :2thumbsup

[tbs]

It could very well be due to the aftermarket pipe you've got on there.

These bikes run pretty lean to begin with, and then when the slip-on is changed it runs even leaner and you get that popping on deceleration. There are long on-going debates over on gixxer.com about whether this is bad for your engine, mostly in threads about cutting off the catalytic converter and fitting a mid pipe. A lot of guys will fit power commanders and get custom fuel maps, but George from Motorcycle Doctors here in Auckland assures me that the stock ECU can be tuned to deliver the right mix for an aftermarket pipe.

You should have a chat to a decent Suzuki mechanic about it.

[fetchfire]

I have a DRZ400sm with a powercore 4 exhaust. It does this all the time.

[rastuscat]

Used to go down the Grafton offramp toward Wellesley Street, hit the kill switch while at a good speed, pause, then turn it back on again.

Man, backfire...........you have no idea. Cleared the senses, I can tell ya.

[BuzzardNZ]

It could very well be due to the aftermarket pipe you've got on there.

These bikes run pretty lean to begin with, and then when the slip-on is changed it runs even leaner and you get that popping on deceleration. There are long on-going debates over on gixxer.com about whether this is bad for your engine, mostly in threads about cutting off the catalytic converter and fitting a mid pipe. A lot of guys will fit power commanders and get custom fuel maps, but George from Motorcycle Doctors here in Auckland assures me that the stock ECU can be tuned to deliver the right mix for an aftermarket pipe.

You should have a chat to a decent Suzuki mechanic about it.

+1 . My SV used to do this after I added after market ( 2 brothers ) pipes. I thought it sounded pretty good actually. Later on I took the
bike in to get dyno/TEKA tuned and they found it was running too lean, so they richened it up at certain rev ranges. Now runs a lot smoother and no back fires on overrun ( damn ). Still, running richer on a v twin sure seems to drain the economy :( I only get about 180K per tank after those mods, used to get around 240.

[BuzzardNZ]

Used to go down the Grafton offramp toward Wellesley Street, hit the kill switch while at a good speed, pause, then turn it back on again.

Man, backfire...........you have no idea. Cleared the senses, I can tell ya.

lol, I've heard an XT500 backfire and that scared the sh1t out of me!!!

[RuoskaNZ]

Took it out again to try and redo it. I guess it just sounded worse than what it actually was when I was zoned in and going hard.
'popping' on overrun ' would probably best describe it, and as long as it isn't doing any harm I cant really afford a remap/dyno tune.

Also, it is inefficient enough as is, maybe get 200km out of it if I go easy as. Not sure what it is supposed to be.

Its not a decent bang, just popping and rumbling.

[ducatilover]

+1 . My SV used to do this after I added after market ( 2 brothers ) pipes. I thought it sounded pretty good actually. Later on I took the
bike in to get dyno/TEKA tuned and they found it was running too lean, so they richened it up at certain rev ranges. Now runs a lot smoother and no back fires on overrun ( damn ). Still, running richer on a v twin sure seems to drain the economy :( I only get about 180K per tank after those mods, used to get around 240.
I dare say a difference that big wouldn't be down to just the tune. That's what, a 25% difference, if you were running it that lean, you probably wouldn't have any valves or pistons :bleh:

[jellywrestler]

Used to go down the Grafton offramp toward Wellesley Street, hit the kill switch while at a good speed, pause, then turn it back on again.

Man, backfire...........you have no idea. Cleared the senses, I can tell ya.
and you're now a policeman? How did you get a badge with a background like that?

[Phantom Limb]

Learn to love it.
Coming down the valley into my home town my 1300 sounds like rolling thunder. Makes a great warning device for coming up behind slower riders, they definitely know somethings coming :scooter:

[rastuscat]

and you're now a policeman? How did you get a badge with a background like that?

I proved I was human. That used to count for something.

[skippa1]

I proved I was human. That used to count for something.

Not now. Even my phone is an Android

[Tunahunter]

My bike's Two Brothers pipe makes a really good backfiring (type) noise, I love it and so do the punters walking over the motorway overbridge on Hill Street Wgtn when I'm decelerating heavily after a big burst out of The Terrace Tunnel

[Fast Eddie]

Used to go down the Grafton offramp toward Wellesley Street, hit the kill switch while at a good speed, pause, then turn it back on again.

Man, backfire...........you have no idea. Cleared the senses, I can tell ya.

hahaha..

you do it on the work bike?

[rastuscat]

hahaha..

you do it on the work bike?

I am stupid at times,but not THAT stupid.........:crazy:

[Oakie]

I am stupid at times,but not THAT stupid.........:crazy:

Hey RC, you guys have ID numbers or something on your helmets? I followed a couple of cars behind a two wheeled popo for a bit yesterday morning and he seemed to have what looked like a number '3' on the back of his lid?

[rastuscat]

Hey RC, you guys have ID numbers or something on your helmets? I followed a couple of cars behind a two wheeled popo for a bit yesterday morning and he seemed to have what looked like a number '3' on the back of his lid?

Well spotted.

We recently put numbers on the rear of our helmets for a motorcade operation. It was a very highly ranked overseas visitor. Our motorcade commander complained that he couldn't tell the difference between us from behind, so we put big numbers on the back of our helmets.

Mines the exception. I just got a new helmet, so no number. I was on one bike yesterday, the other bike rider was another full time rider who was working. He has the 3.

We are quite different to the educated eye, but to many we all look alike. Yesterday a bloke walked up to me when I was parked doing some paperwork. He told me he had almost flipped me the bird, coz he thought I was one of my other riders, a mate of his. Ya gotta love a sense of humor. ;)

[Oakie]

So if we see a two wheeled popo with no racing number on his lid we can give you the old KB wave?

EDIT. On second thought that won't work as we'll be behind you. I know, we'll just catch up and give you a wave as we overtake ...

[rastuscat]

So if we see a two wheeled popo with no racing number on his lid we can give him the old KB wave?

EDIT. On second thought that won't work as we'll be behind you. I know, we'll just catch up and give you a wave as we overtake ...

Be careful. One of my guys was injured in a crash back in March. He will be back riding in maybe Nov. he wasn't on the numerical motorcade, so his helmet looks identical to mine. System 6 BMW helmets in white.

The stripes are a clue. I wear 3, each of my guys wear 1.

Flip me the bird any old' time. I've got a thick skin!

We change bikes at times too. I normally ride 56 when I'm working, the other is 59.

Stop me for a chat, you might be surprised how much we have in common.

[Oakie]

Stop me for a chat, you might be surprised how much we have in common.

Don't think I'd be surprised at all. I've always got on pretty well with popo. One even offered to take me on patrol one night when I was writing an article for the local newspaper. Fun times. The highlight was him pushing me through a bathroom window to get access into a house when the person renting it for the weekend had not been able to pick up his keys. (Yes we checked it was a kosher rental first).

Thought from time to time about stopping and saying hi to a bike popo but wondered how I'd start that conversation:
"Hi, are you RastusCat?". Do the other bike popo know your alter ego? Could be bad for me if they didn't. Three stripes though. I'll remember that.

[Conquiztador]

Back to the issue.

A few ideas:
- 98 octane is made for high compression engines and will burn slower than 91 octane (98 octane has stuff added so it does not burn too fast). There is a possibility that if you use 98 octane the fuel does not have time to burn.
- A leak in exhaust (small hole or poorly connected header pipes) can allow air (and therefore oxygen) in to the exhaust allowing for any unburnt fuel to be ignited by hot header pipes and therefore causing the backfire.
- Exhaust valve leak (caused by seat wear or cam timing issues) could also allow fuel in to the headers.
- Crappy spark plugs maybe?
- And ignition timing (too late) might also cause unburnt fuel to get in to headers?

All this is based on carbi engines so might not be directly relevant to EFI ones?

I agree with a earlier poster: Take her in to get new plugs and tuned and I suspect you will have it all sorted.

Good Luck!

[rastuscat]

Back to the issue.

A few ideas:
- 98 octane is made for high compression engines and will burn slower than 91 octane (98 octane has stuff added so it does not burn too fast). There is a possibility that if you use 98 octane the fuel does not have time to burn.
- A leak in exhaust (small hole or poorly connected header pipes) can allow air (and therefore oxygen) in to the exhaust allowing for any unburnt fuel to be ignited by hot header pipes and therefore causing the backfire.
- Exhaust valve leak (caused by seat wear or cam timing issues) could also allow fuel in to the headers.
- Crappy spark plugs maybe?
- And ignition timing (too late) might also cause unburnt fuel to get in to headers?

All this is based on carbi engines so might not be directly relevant to EFI ones?

I agree with a earlier poster: Take her in to get new plugs and tuned and I suspect you will have it all sorted.

Good Luck!

Well informative post.

Is it the same with the V8 super cars? They spew flames out on deceleration, and they are surely fuel injected. Guessing they don't burn all the fuel that gets pumped into the system, and that the exhaust gas is so hot it ignites on the way out.

Ta for getting us back on track.