How to cure backfiring?

[SVrider24]

Story:

I took the bike out for a spin today, hasn't been on the road in a week.. new clutch cable,HID lights,and lower fairings..(has a yoshi pipe)...and its been crackling on decel and the ODD *POP* for the past month (but no BANGS).
So today i begin Engine Braking @ a stoplight and it goes BANG.... BANG.. n im like..wtf.. n i take off n it doesn't do anything, decel again n it does one pretty loud POP.. and i think my issue is getting worse! =(




Action:

I searched for some posts about backfirings and I have to do something! But..what number of the following things could it be (and can i do some myself?)





Information:
(2002 Carborated Sv650s 12,000k(hasn't been tuned since 5000k)



Possible Causes of backfiring:


Exhaust Leak (Yoshimura Rs-3 Pipe)
Out of Sync Carbs
Non-Adjusted Valves
Dirty Carbs
Too Lean (due to Exhaust)

[RonnieRev]

Try riching up the idle/low speed carb circuit, you can try the mixture screw's if that doesn't help, try a larger pilot jet.

[djltoronto]

From another site:



Deceleration Backfire is caused by fuel burning in the exhaust manifold or header.

No ifs ands or buts, that’s what causes it. But the bigger question is how does gas get there in the first place, and that’s a bit more complicated. Generally, there are a variety of ways it gets there, and a variety of things that can make the backfiring worse. But there’s a kicker, and something you should understand before we go any farther:

A motor in perfect tune will exhibit deceleration backfiring.

Therefore, just because your motor is banging it up, doesn’t mean there’s anything wrong. And consequently:

Getting rid of the noise means de-tuning your motor.

Yup. If you’ve jut got to eliminate that popping, you’ll have to accept the fact that your motor is going to be forced to run rich to do it, and that isn’t necessarily a good thing. So lets talk about what causes the problem.

Ok, so you’re riding along at some given rpm, and suddenly you decide to decelerate, and you reduce the amount of throttle. This causes an “overrun” – that is, the motors rpm is turning faster than the fuel provided can support, so the motor begins to spool down. This causes a couple of things to happen.

First, when you close the throttle, you are also closing the throttle plates. This reduces the air and fuel flowing into the motor, and increases the vacuum (lowers the pressure). This results in less air and fuel in the cylinder during the power stroke, which in turn results in a lower pressure in the combustion chamber. Remember I said earlier, that the A/F mix burns faster in proportion to the pressure applied? Well, when we reduce pressure this way, the mix burns slower. This results in two things happening.

1. The lower burning fuel generates less heat, and the cooling effect of the non-burning fuel tends to “quench” the flame front, or slow it down even further. Because the mix is burning much slower, the exhaust valve can open before all the fuel is consumed, and the unburnt fuel is ejected into the exhaust.
2. The engine designers, in order to promote smoother idling and better combustion, retard the spark when the throttle is shut, and this results in the mix being lit later.

So, now we end up with unburnt fuel in the exhaust, and burning fuel being ejected into the exhaust, and bang! Backfire. In addition, Honda has added a device called a “programmed air injection valve” (Pair Valve) that actually injects some fresh air into the exhaust to help this process along – since fully burning the fuel results in cleaner exhaust. So the backfiring is not only a normal part of the engines operation, it’s also intentionally amplified by Honda! Of course, normally, that massive bazooka pipe Honda hangs on your bike hides most of the noise, but it’s there, even when you can’t hear it.

So the bottom line, is: That backfiring is perfectly normal and expected. If you’ve just got get rid of it, that’s up to you. You’re entitled to set your motor up the way you want, and your goals are your goals. But don’t refer to it as “fixing” the popping. Rather, the correct way to think of it is “de-tuning a bit to get rid of the popping”.

[RonnieRev]

Kevin, you say your bike back fired more today then in the past. The cold temp effects the fuel mixture, the colder it is, the leaner your bike will run.
You will aways get some popping on decell, but it shouldn't bang. Wait for some warmer temps and see how it is.
The aftermarket pipe will make the engine run leaner.
Maybe a D.J jet kit will help you out

[SLIM]

Perhaps a foolish generalization, but - you sure it isn't just a v-twin thing? My VTR backfires and pops like crazy when decelerating. It's normal for the bike.

How about getting together with a few other SV650 riders to compare? Maybe what you think is strange is really normal for the bike.

[toastman]

weak battery and fouled plugs will also do the backfire routine

[RonnieRev]

Its some what normal on a stock bike because the factory jetting is very lean to make sure its in the EPA standard's.
The first mod in any jet I have seen is to remove mixture screw plugs and crank out the screw to richen it up.
Add the full pipe to factory setting's and you have a lean running engine.

[taxnatural]

i think its the V-twin in the cold

[1LTRK6]

my bike use to backfire a lot , since i removed K&N filter and put stock one back works better, i would hear pop one in a while and thats it... Also I have to do tune up anytime soon...

[slowbird]

Tuesday night I was riding home and it was pretty chilli out.

Whenever I'd engine-brake/decelerate I could her the exhaust pop quite a bit.

Doesn't do it much when it's warmer out.

[MarcosSantiago]

Are you inclined to do work on your bike?
Do you have the space to work, and some basic tools?
It's time to dig in there...

You keep posting questions about different symptoms of the same problem.

Tostart, you need to remove the carbs, and do these two things FIRST:

• Adjust the air/fuel mixture, so it is exactly the same on both carbs
• Shim the needles

Go to www.svrider.com for instructions in how to do this.

If that doesn't resolve the problem, rejetting is next.

If you have questions... I'll try to answer...

[amp3d]

edit, wrong link ill repost

[Yamaha_Gurl]

Backfiring is awesome! I love it! My TL has two custom cut Yosh pipes, and when it back fires everyone hears it...and notices the blue flames coming out of the exhaust, I knew have issues with riders following too close

[SVrider24]

Backfiring is awesome! I love it! My TL has two custom cut Yosh pipes, and when it back fires everyone hears it...and notices the blue flames coming out of the exhaust, I knew have issues with riders following too close

Personally I agree to the sound of it...but the fact I know that that sound is telling me I mis-fired, makes me worried that if continued I'll damage my engine

[RonnieRev]

You wont damage your engine

[Froglet]

My Ninja 650R is a parallel twin and I've installed a Scorpion Slip-on Exhaust. On my bike, removing the stock pipe also removed the Catalytic converter. I don't know whether yours is still on....I'm not familiar with yours.
So, now the bike runs much leaner and I'm getting the same popping you are describing. Now, it's not that much and I can almost control it, but there is something that can be done to reduce that popping. Probably a Power commander or even plugging the PAIR Valve, which becomes useless when the Catalytic converter is removed...it is just an emission control device.
See the link below, and click on Pair valve to get an idea. http://www.fortycaliber.org/
I've decided to leave mine alone, for now.....it's not that bad.

[timyates519]

Gix does it on command. Sounds like a gunshot... alot of fun when passing by wannabe gangsters on the sidewalk.