I doubt it's any big deal. Was the 600 exhaust you mentioned aftermarket or stock? Is the backfire a "cough" through the airbox? or just a burble/pop from the exhaust? Most aftermarket cans will pop a bit on decel (and I actually kinda like it), and there's much less harm done to a motor from running rich compared with running lean...

 

not sure if this actually works but i heard you can plug of the PAIR valves if you have an aftermarket pipe to get rid of the pop on decel. no idea if its true or not.

 

mmy PAIR mod i did on my 6 actually made it back fire some.

but mine does it occasionally as well. i'm running a gix 1k header and a bolt on can. i'd just get a full 750 system for the bike and a PC with map and enjoy a good solid 130hp from the thing.

 

Sounds good. I wasn't overly concerned, but glad to know it was a common thing. And to answer the question it was/is a pop from the exaust. Thanks.

 

The PAIR valve is simply a reed valve that Suzuki put on the bikes to keep the emissions down. It works by allowing fresh air into the exhaust stream as the gasses leave the cylinders, any unburned fuel is further combusted as it travels through the exhaust system. When you quickly close the throtle you cause the air/fuel mix to go very rich for only a moment. The ECU usually compensates but it still takes a split second to catch up. Because the A/F is so rich a lot of unburned fuel leaves the cylinder, when the PAIR valve does it's job...POP!!! Thought you might like to know. Blocking the Pair valves or removing them, doesn't give you more power, It might eliminate the backfires but your bike will smell pretty stinky because of all the unburned fuel. Don't worry too much about an occasional backfire, now if it's happening every time you roll off the throttle, start worrying.

 

actually its a control valve that keeps new riders who can't handle the power of these racing machines. it delays part of the explosive power that these machines make for the first few gears. Only a handful of us REALLY know - that if you eliminate this restictive device, it'll give you instaneous power throughout the powerband, thus increasing your overall performance and puckerfactor.

 

How could I have been so wrong, Thank You Gimpsta-San for showing me the Way. Now I must go practice my Squid Style Kung-Fu

 

isnt backfire involving fire shooting back into the intake.

and afterfire is fire coming out the exhaust

 

isnt backfire involving fire shooting back into the intake.

and afterfire is fire coming out the exhaust

I don't know... I always just called it a "cough" through the airbox when it does that.

Either way, he said it's the exhaust that was doing it, not the intake

 

The backfire is due to to much fuel being sent to the combustion chamber on decelleration. If you set your 0%, 2%, 5%, 10% fuel settings at the RPMS you'er having backfire problems with less fuel and go from there you should be fine.

 

My mechanical knowledge is very limited to say the least. In any event my bike was doing the same thing...Backfiring on decel. I took the bike back to the dealer i brought it from & they still couldn't pinpoint the problem. Luckily a short time later the FI light came on. I got the bike back to the shop, & it turned out that the throttle bodies were not working correctly. They had to be replaced....My bike was still under warranty, so they were replaced free of charge. The one thing that really concerned me before the FI light came on nobody at the dealer had an "F" ing clue what was wrong with my bike.

 

as the one guys said before, backfire is a pop through the intake. an afterfire is a pop from the exhaust. i have a full yosh rs3 with a power commander and map from their website and it still afterfires on decel in high rpms. it will pop like a gun just went off and shoot like a 1 foot blue flame out the exhaust. i even had a friend video tape it on his camera phone when i was running my bike on the dyno. its seems normal for an aftermarket pipe to do that and i dont see any problems from it. if you had a backfire through the intake though, that would be a problem as it will push your fuel/air mixture back to the airbox.

 

I blocked off the pair valve on my SV because it did sound like a gun firing. I like the sound much better now that it's blocked. Once I get an aftermarket pipe on my GSXR, I will probably do the same. It makes it sound much better IMO without all the popping on decel.

 

How do you block off the pair valve? Safe to do?

 

I haven't done it yet on the GSXR but on my SV there was a small tubular plastic cylinder that came up through the bottom of the air box. This is where the PAIR valve drew the fresh air from. I found a bolt that matched the hole, put some RTV on it, and screwed it down into the hole. So now, no more air can go through. That is the easy way. Some other people sell kits that you can remove the whole PAIR setup but what I described above is the easiest way. Again, I haven't even opened up the airbox on the GSXR yet but I would bet it's similar. Someone can correct me if I'm wrong.