Backfiring like crazy

[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

[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

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

[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