Backfiring / backfire

[eyesspee]

All,

I've searched backfiring / backfire and come up a blank on what I want to know.

My bike (CBR 600 F3 - carbied, not injected) backfires when engine braking after a period of hard accelerating. i.e. give it a blat in first up to 9,000rpm then just let it coast and it will usually backfire once, sometimes twice as the engine slows down. Other times it might be a blat in 4th. The commonality to the backfire is it happens while engine braking after 'giving it some'. I am of the impression this is because it's running rather rich ....

Anyway I'm by no means a bike expert, but have several questions:
1. Is this normal?
2. If answer 1 is no, then, is it worth worrying about?
3. If answer 2 is yes, then might it be simply a matter of running a bit rich (which I believe to be the case)?
4. If answer 3 is yes, is it difficult playing with the carburettor to adjust the fuel mixture? I've played with other carburettors and usually fucked things up moreso by just touching them. They seem rather complex devices ...

If somehow the answer isn't above, does anyone have any suggestions? I've replaced the air filter (not because of this, just routine maintenance) and have tried normal fuel and BP ultimate with the same results. The can is stock.

Should I just got to MDH and get a tune up and see if that works?

Cheers for any help.

[shlacks]

id say idle jets are too rich causing excess fuel with closed throttle
but im no way a expert on carbys

[Rhino]

Backfire or burnoff... ?

Just some unburnt fuel detonating in exhaust system rather than engine...

Or is it loud like the muffler is going to peel back like a banana - loud?

My car 'pops' when I back off and the engine braking kicks in as you describe... I wouldn't think that it is anything to be too concerned about.

[Magenta Tiger]

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[eyesspee]

Originally posted by S2-Ahh@Jan 9 2006, 08:25 PM
Backfire or burnoff... ?

Just some unburnt fuel detonating in exhaust system rather than engine...

Or is it loud like the muffler is going to peel back like a banana - loud?

My car 'pops' when I back off and the engine braking kicks in as you describe... I wouldn't think that it is anything to be too concerned about.

[snapback]211888[/snapback]

Umm ... well I wouldn't call it banana peeling loud. I've watched my mates intentionally backfire old bombs by turning off the ignition and gassing the accelerator several times and they're LOUD. This is nowhere near as loud, more a pop as you say ....

To clarify, this popping occurs about 1 or 2 seconds after I start to back off, not straight away.

I've had the bike 6 months and it has done it consistently since I've had it and it hasn't got any better or worse - stayed as the same type of pop. Other than the air filter and types of fuels, I haven't touched anything.

[Jonchilds]

Popping is just unburnt fuel in the exhaust - common on carbied motors running a little rich. Can also be caused by running overly rich and causing a misfire at high RPM.

Backfiring is actually flames/fuel coming back out the carby (from my experience) and can damage the motor.

A loud BANG from the exhaust is ok occasionally, but it will eventually see some damage done to the exhaust (atleast on a car).

[MoreHPLessKg]

Originally posted by Jonchilds@Jan 9 2006, 09:13 PM
Popping is just unburnt fuel in the exhaust - common on carbied motors running a little rich.* Can also be caused by running overly rich and causing a misfire at high RPM.

[snapback]211922[/snapback]

Although happens in injected bikes. Dont know anything about mechanics of it or anything but my bike does it, Ive seen jenna's 05 R6 shooting blue flames and jono's R1 shooting blu flames.

[Jonchilds]

Originally posted by MoreHPLessKg@Jan 9 2006, 09:17 PM
Although happens in injected bikes. Dont know anything about mechanics of it or anything but my bike does it, Ive seen jenna's 05 R6 shooting blue flames and jono's R1 shooting blu flames.

[snapback]211926[/snapback]

Put a cat-converter in and it should go away <_<
It&#39;s just unburnt fuel in the exhaust. Engine breaking conditions with low compression aren&#39;t the best for setting things on fire, and the injectors may be under-loaded (? not sure) leading to a rich condition.

[CB Boy]

Originally posted by Magenta Tiger@Jan 9 2006, 08:28 PM
Any leaks in the headers or collecter to the pipe can also cause it, Might pay to check that before giving it to Mark.

[snapback]211893[/snapback]

What he said.

When i&#39;m running the stock can on the CB where everything is a nice snug fit, all is well

When I swap over to the Yoshi, where the link pipe does not have a tight seal with the can, it pops and burbles and carries on when I back off the throttle.....the higher the revs, the more popping.

I call it character

[shadowrider]

Originally posted by Jonchilds@Jan 9 2006, 09:24 PM
Put a cat-converter in and it should go away <_<
It&#39;s just unburnt fuel in the exhaust.* Engine breaking conditions with low compression aren&#39;t the best for setting things on fire, and the injectors may be under-loaded (? not sure) leading to a rich condition.

[snapback]211930[/snapback]

not having a go

all a cat converter does is burn unburnt hydrocarbons changing the gas from carbon monoxide to carbon dioxide , the excess fuel will accually damage the cat, never mind the fact that they are very expensive.

a few peeps are close to the mark, it sounds like the bike just needs a tune up

[MoreHPLessKg]

Originally posted by shadowrider@Jan 9 2006, 09:47 PM
a few peeps are close to the mark, it sounds like the bike just needs a tune up

[snapback]211954[/snapback]

My bike rarely "pops" anymore since I installed the PCIII and the right map for the zorst. Same thing

[tigerleo]

When I read up on this a couple of months back when I de-baffled my Suzi (causing it to backfire considerably) there were a couple of things I found out:

1. That the back firing after closing the throttle is due to a lean fuel mixture rather than rich - not much to worry about and is common with a well designed system (the backfiring).

2. As Marty said, it adds character

3. The idle mixture (usually the one you can adjust easily on the carb) only adjusts the idle, hence it&#39;s name - you can richen the fuel mixture which will reduce the backfiring as when you close the throttle there is more fuel getting through, hence not a lean unburnt mixture that has escaped to the pipe and then detonated there.

Hope that makes sense - that is how I understand it.

[Jamathi]

Originally posted by tigerleo62@Jan 9 2006, 10:40 PM
When I read up on this a couple of months back when I de-baffled my Suzi (causing it to backfire considerably) there were a couple of things I found out:

1. That the back firing after closing the throttle is due to a lean fuel mixture rather than rich - not much to worry about and is common with a well designed system (the backfiring).

2. As Marty said, it adds character* *

3. The idle mixture (usually the one you can adjust easily on the carb) only adjusts the idle, hence it&#39;s name - you can richen the fuel mixture which will reduce the backfiring as when you close the throttle there is more fuel getting through, hence not a lean unburnt mixture that has escaped to the pipe and then detonated there.

Hope that makes sense - that is how I understand it.

[snapback]211999[/snapback]

I have set my iddle on purpose a bit high so that my CBX does this on closing the trottle and engine braking.
I frikkin love it after the howl on reving it.
The tunnel is by far the BEST place for this sort of serenading.
It is just a slight crackle like the real 6 cil Honda race bike and also the old MV&#39;s on full song
Old Carbie bikes rock with no plastic in sight, ahh well not much anyway.