backfiring

[purplefalcon]

help, i have taken the cans on my '04 and drilled 6- 1/2" holes in the front and in the rear, sounds pretty nice, but now i am picking up a backfire......sounds like it is right at the heads and is a very random occurance. it happened last several times on a 100 mi. ride last night and only occurs just as we come to a complete stop at intersections, but not all intersections.
on the highway the bikes' extremely smooth and seems much more linear, but i am thinking that i have drilled so much, that i must be approaching having put on aftermarket cans and may need a remap, like maybe the low speed circuit is too rich ?
any first hand experience with this matter will be greatly appreciated, as i am afraid i am going to start blowing out gaskets...........or worse.
damn, my wife was right again ..... stock is beautiful.

 

[PureEnergy]

Mine did that after I drilled the holes too...  just a bit of backfiring from time to time when I'd come up to a stop light, etc... never ever did it at higher rpms or on highway, etc.     It did sound pretty good though, but like you I didn't want to hurt the engine...  

About 2 weeks ago, I got a great deal on a used Micron full exhaust system installed it and don't have any backfires at all now.    I've just added the Powercommander PCIIr and the whole bike is much smoother and runs better.   Also, still no backfires...      

Sorry I can't tell you if a PCIIIr will fix your problem, but by just changing to the Micron  my backfiring went away...

 

[purplefalcon]

thanks, given that i'm on a wifey imposed budget, and can't afford the rs3 yoshi cans, i think i'll go back into the outlet end of the cans tonight and try plugging 3 of the holes in each can.

the back firing must have something to do with there being little or no back pressure or the flow isn't always consistant and builds up too much back pressure..............what a pain.

anyway, this should suffice as a word to the wise about getting crazy with your drills.

 

[Johnnycheese]

Plug the PAIR off and the backfire will be gone

 

[Juggler]

Johnnycheese,
You're the resident expert, so I'll ask, why does the PAIR valve mod fix this problem?

 

[purplefalcon]

PAIR ? wuuzat ? is this for real ? talk to me.

 

[Johnnycheese]

the Pair injects cold air into the exhaust system (same as an air pump on a car).
it does two things
1) is it fools the epa into thinking the exhaust is cleaner than it really is.2) the main reason is it burns unburnt fuel before getting out into the air.
but without a closed end muffler like stockers the fuel travels further back and the PAIR air burns it to close to the exit of the tail pipe and you get backfire. plugging the pair will not burn the fuel anymore thus backfires stop.
on some you also need to add more fuel to get it to stop

 

[bbbsleeper]

the Pair injects cold air into the exhaust system (same as an air pump on a car).
it does two things
1) is it fools the epa into thinking the exhaust is cleaner than it really is.2) the main reason is it burns unburnt fuel before getting out into the air.
but without a closed end muffler like stockers the fuel travels further back and the PAIR air burns it to close to the exit of the tail pipe and you get backfire. plugging the pair will  not burn the fuel anymore thus backfires stop.
on some you also need to add more fuel to get it to stop

Exactly, I have never had any backfires from this mod. But about two weeks after I got my bike the PAIR was gone.

 

[purplefalcon]

you guys are great, thank you.

if i'm reading this right, i can remove, cap off, or in some fashion do away with the pair and at the same time may not have to remap for more fuel ?