I got my Yoshimura (CF) put on this weekend. I've noticed that now on abrupt off-throttle action, the bike will backfire a bit. Small popping sound, nothing terrible but the stock exhaust did not do that. Normal?

My vote is NORMAL.

Check for any leaks in the exhaust system,

 
This is perfectly normal, happens when we change exhausts. Its the air being pushed into the exhaust chamber by the emmisons air pump. You can order block off plates or just plug off the hose from the air pump. Im sure that someone on here has done so on the fz07 and will chime in.
 
 

I got my Yoshimura (CF) put on this weekend. I've noticed that now on abrupt off-throttle action, the bike will backfire a bit. Small popping sound, nothing terrible but the stock exhaust did not do that. Normal?

 

Yeah my delk exhaust pops quite a bit I think it sounds cool.

Don't think the FZ-07 has an air pump for emissions.

This is perfectly normal, happens when we change exhausts. Its the air being pushed into the exhaust chamber by the emmisons air pump. You can order block off plates or just plug off the hose from the air pump. Im sure that someone on here has done so on the fz07 and will chime in.
 
 
I remember reading the FZ-07 did not have back off plates like the FZ-09?

 

YZetc, ya beat me to it!

Happens.

It's my dang typing skills, slows me down.... (rofl)"

Totally normal. I'm a fan of it.

Dobeck said somewhere that the cause of that is air being pulled into the exhaust inbetween firing pulses. Fresh oxygen, heat and unspent fuel vapors combine to create the popping. They called it... reversion.

Some kinda like the sound.

I believe this happens even with the stock exhaust, but is more muffled.

See, that's what I was thinking. That the large chambers of the stock exhaust masked the sound. OK, cool. I was thinking I may have left out a part ....
 
I do love the new rumble, huge grin now hitting the start button!

It's normal. It's your bike's way of crying because you're getting off the throttle. I have Akra with baffle removed and some people say (that have this setup) it does it often... mine does it rarely. Maybe they don't have a fuel controller. I like it though wish mine did it more.

It's normal. It's your bike's way of crying because you're getting off the throttle. I have Akra with baffle removed and some people say (that have this setup) it does it often... mine does it rarely. Maybe they don't have a fuel controller. I like it though wish mine did it more.

Interesting.  It has always been my impression that this sort of popping coming off throttle was a result of a lean condition with the fuel mixture.  That's why we check for air leaks - right ? Lean = Hot = Bad.  So, in my mind, installing a fuel controller and enriching the mixture would possibly decrease the popping - just like rejetting carbs would do.  But isn't that what the O2 sensor does?  Somebody set me straight! 

The popping is usually due to un-burnt fuel in the exhaust,
if air then gets into the exhaust from air leaks or air injection
that fuel then burns and you get the popping.
My 07 don't do it on the standard exhaust but my old Morini sounds
like the gun fight at the OK corral on the overrun.

@ralph and @hobbs got it correct. Reversion. The configurations of the Dobeck are awesome so you could feed it more fuel during a certain stage and in that case it might have left over gases. My comment was directed to the Akra setup and if there was no fuel controller, the misconfiguration of the air/fuel might do this as well. However, I can't speak on behalf of Akra without db and no fuel controller as I do have a fuel controller setup in mine.
 
 
 

If it really bothers you, try hi-temp RVT at the exhaust joints to stop any fresh air from being pulled in. If mine does it, that is what I am going to try.