"Backfire" with aftermarket exhaust

[The Snowman]

I recently purchased a used '97 CBR900RR that has a Two Brothers full exhaust, K&N filtercharger and was rejetted.

The question I have is that when I come down in RPM, especially from say 7K - 2K quickly, the bike seems to backfire. It doesn't bang, or throw flame, it just crackles.

Is this normal, or is it a sign that I might have the wrong jetting in the carbs?

[bigred875]

sounds pretty normal....

[The Snowman]

Actually, it sounds almost like the other Backfiring Thread going.

[union]

Sounds pretty normal to me. Mine backfires a bit as well. Sounds like shotguns going off. I cant say for your bike but on the RC51 there is a mod I can do to prevent this I just havent done it. Id imagine if you looked around enough there might also be a mod for you to do.

[tls25rs]

There is a chance that there is air getting into your exhaust through one of the slip joints or possibly a loose fitting at one of the exhaust ports, that is then reacting with some unburned fuel that might be getting into your exhaust on deceleration due to jetting inconsistencies, which would in turn cause the popping type backfiring you are experiencing. Check your exhaust and make sure all the flanges at the head are snug and that all the slip joints are tight. If all of this is OK then you may be getting an inordinate amount of fuel into your exhaust causing the backfires.

Not that I know anything but this is my best guess.

Good luck

Joel

[Doc]

What ta heck you Jacked mt Thread!!


I am gonna check for leaks, that may be the cause.

[The Snowman]

Originally posted by Doc
What ta heck you Jacked mt Thread!!

Funny thing is that we both posted within 15 minutes of the other about the same subject. But you did post first.

Someone hit the thread consolidation button.