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-   -   Deceleration popping (https://www.zxforums.com/forums/zx-7r-forum/21981-deceleration-popping.html)

JasonX7 05-13-2009 05:53 PM

Deceleration popping
The last owner put a DnD slip-on and the bike just pops and gurggles like crazy. My R6 used to do it with its Micron, but it only popped every 3 or 4 seconds. My ZX7 is gurgling unattractively and smells lean (not rich :p ). How would I stop this nonsense?

Chief 05-13-2009 06:42 PM

Do the KLEEN Mod and eliminate the emissions. Once I did that to mine the backfire stopped.

JasonX7 05-13-2009 07:01 PM

Is that the sole reason for the back firing? or is this just a work-around? I'm sure if theirs that much unburn fuel getting into the pipe, then I would assume that the bike needs some tuning to prevent unburnt fuel from getting their in the first place.

I'll still probably do the mod, just cause I can :tard, thanks.

Shifty1 05-13-2009 08:26 PM

Carb adjustment should do the trick. You're running rich...lean it out a bit and see how it works.

mjw1 05-13-2009 09:15 PM

If your bike is popping on deceleration it means you are running lean not rich. Go one size up on your pilot jet or eliminate the smog and do the carb mods.

suprajztwenty 05-14-2009 12:06 AM

i thought that performance exhausts make the mix go lean...if you dont have a jet kit installed, you can tune your air fuel with the pilot jets...search pilot jet and learn where theyre hidden. its a little complicated for the average lube technician, but if you can drill a hole (slow and patiently) taking the tamper proof caps off is the only tedious part.
turning the screws in will lean it out, turning them out (counterclockwise...or lefty loosey) will richen it up. stock setting on a 96+ is 1-3/4 turns out from bottomed out. jet kits ask for 2 to 2-1/2 turns out (depending on altitude) while youre in there check the float height, you could have 1 or 2 off spec.
service manual link...itll fill in some gaps
http://www.carlsalter.com/download.a...41046112100102 when pdf opens, enter motocd for the password

definatly do the float bowl mod regaurdless what parts you have installed, it makes the bike feel healthier

Hammerhead 05-14-2009 03:06 AM

They do, and here's how: During overlap, the short period of time when the intake valve is beginning to open and the exhaust valve is not fully closed, the greater inertia of the exhaust charge from the freer-flowing aftermarket pipe sucks some of the incoming charge into the exhaust. The mixture in the combustion chamber is effectively leaned out since some of what would have been trapped inside has been sucked past the exhaust valve. Only during decel does enough mixture build up in the pipe to cause the audible pop.

suprajztwenty 05-14-2009 10:08 AM

yea, faster flow=better exhaust scavenging...so basically its always gonna do it?...but with a richer mix, could it potentially shoot the flames out the tail?? thats just cool

JasonX7 05-14-2009 12:46 PM


Originally Posted by suprajztwenty (Post 151059)
yea, faster flow=better exhaust scavenging...so basically its always gonna do it?...but with a richer mix, could it potentially shoot the flames out the tail?? thats just cool

I wish I had a video of my R6 deceling in 1st gear from top RPM.

The bike would straight up shoot fire out of the highmount. My friend was behind me on his GSX-R and said that the pipe would act like a machine gun sometimes. It would shoot flames out like gunfire, and one time I saw a BIG one in my rear view! When I'm deceling less aggressively, the bike would sometimes shoot out a blue flame at nighttime.

It sounded great and popped like something in the fast and furious. Something like that can't be healthy can it? Anyways, I sold the bike to get something less of a beater (it was stunted and abused before hand).

Anyways, I can't wait till summer, since usually I get home from school 7-3 and work 4-8.. So I'm going to do so much shit to this bike when I have that time on my hands. Thanks for pointing me in the right direction, everyone.

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