How can I tell if it's a backfire or just pops & bangs

[.blue]

My bike has always made little explosion noises when decelerating. Very cool, like it a lot.

It's got an aftermarket exhaust since before i bought it so I've always thought this was normal for the set up.

But how do I know this isn't actually a more serious back fire?

PS have read this (http://www.pistonheads.com/gassing/topic.asp?h=0&f=69&t=1201250&mid=162518&i=20&nmt=Why+does+my+exhaust+pop+and+bang%3F&mid=162518) but still not sure.

[moto_traxport]

I'm sure someone will be along in a minute to ask what bike it is, what type of exhaust is fitted (slip on or full system) and whether any modification has been made to the fuelling.

[gsxr renegade]

.blue said:

My bike has always made little explosion noises when decelerating. Very cool, like it a lot.

It's got an aftermarket exhaust since before i bought it so I've always thought this was normal for the set up.

But how do I know this isn't actually a more serious back fire?

PS have read this (http://www.pistonheads.com/gassing/topic.asp?h=0&f=69&t=1201250&mid=162518&i=20&nmt=Why+does+my+exhaust+pop+and+bang%3F&mid=162518) but still not sure.

An actual backfire is noticeably different to the little pops/crackles you might get on the overrun. Although your pops/cracks might be relatively loud an actual backfire is a really, really loud ‘bang’. You’d notice the difference.

I’ve only ever had one backfire when I accidentally hit the killswitch while riding along on an old R1. The bike started to die, so I pulled over, noticed the killswitch, so flicked it back to ‘run’ and cranked the engine. The resulting backfire made me jump out of my skin.

[Raize]

Just unburnt fuel burning off in the exhaust.
If you had a backfire you'd know.

[The Beaver King]

You'd know if it was backfiring.

There was a bike that past by our old house most nights, usually around 9pm.

As he approached the corner and started to slow down, you could hear the backfire.

It sound like a fking gunshot!

[Jazoli]

My bike pops and bangs loads on the overrun, and snaps and crackles with the baffle out, it's all down to the AIS or air injection system which bleeds air into the exhaust for emissions reasons, has your bike got this? A lot have these days.

[Tall_Paul]

Completely normal. As already said, it's the unburnt fuel getting towards the end of the exhaust and igniting when hitting the air (oxygen). Pops/burbles/flames on the overrun, all normal. Very different from a backfire which is like a balloon popping, only 100x louder.

[graham22]

Jazoli said:

My bike pops and bangs loads on the overrun, and snaps and crackles with the baffle out, it's all down to the AIS or air injection system which bleeds air into the exhaust for emissions reasons, has your bike got this? A lot have these days.

More than likely this.

Sounds fun to start with but annoying after a while. Got rid of the system (KTM call it SAS) on the SD, the blanking plates saved on a hell of a lot of kit too.

[LeftmostAardvark]

I'm in the same boat (Victory Vegas 106ci). Loads of pops, bangs and cracks but it is meant to be a 'feature' of them as standard. The general wisdom is to get a Power Commander and a dyno run, which is my next step (although I'm probably going to get an auto tune instead of the dyno as there are a few bits I want to do to the bike over the next few months, like an s&s air intake), each of which would need another dyno run.

[Mastodon2]

It seems to be often recommended to blank the air injection off when putting an aftermarket exhaust onto a bike, but short of getting a more accurate gas sample for dyno tuning there doesn't seem to be much tangible mechanical benefit. That said, I work with a bloke who has an older Bandit (no cat as far as I can tell) and a Fuel end can, the pops and burbles are ridiculous. I like a bit of pop and crackle, but his bike sounds daft, he's just pulling out of the work car park and it sounds like he's coming down the gears for the hairpin at Suzuka.

[moto_traxport]

Mastodon2 said:

It seems to be often recommended to blank the air injection off when putting an aftermarket exhaust onto a bike, but short of getting a more accurate gas sample for dyno tuning there doesn't seem to be much tangible mechanical benefit. That said, I work with a bloke who has an older Bandit (no cat as far as I can tell) and a Fuel end can, the pops and burbles are ridiculous. I like a bit of pop and crackle, but his bike sounds daft, he's just pulling out of the work car park and it sounds like he's coming down the gears for the hairpin at Suzuka.

Air leaks on the system are quite good for pops and bangs. Loosen off a slip on can and they generally do it. I'm constantly going back and forward between my standard can (c/w nice clamp and graphite packing) and a race can (which just slips on and I should use a bit of silicone and can't be bothered) and it pops and bangs a treat with the air leaks that introduces.

[.blue]

Thanks for all the replies. Going to say it's not a misfire after checking out some vids and realising how loud misfires are. Appreciate the help

[rodericb]

LeftmostAardvark said:

I'm in the same boat (Victory Vegas 106ci). Loads of pops, bangs and cracks but it is meant to be a 'feature' of them as standard.

They should have called it the Victory East LA

Gee we used to have fun doing backfires in the olden days. Couldn't do them nowadays - thanks terrorism....