Decel Popping...What exactly is the problem with it?
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Tourer
Joined: Mar 2008
Posts: 250
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From: SouthWest Iowa
Decel Popping...What exactly is the problem with it?
Not too many threads on the search on this issue regarding what it is and why it is bad. Many of the ones I found were dealing with p/c or sert etc and fixes. I have an 07 FXDB with BigShots. Decel in 2nd 3rd and 4th at pretty consistent points on the speedo produce some popping. Why I am asking for some feedback here is that its not obnoxiuos and dramatic and I think it sounds kinda cool. So is ita concern and when is action needed?
Road Captain
Joined: Dec 2005
Posts: 534
Likes: 35
From: Western Australia
RE: Decel Popping...What exactly is the problem with it?
I don think it does any harm if you leave it, but you can get rid of it if you want. Your SERT needs to give a bit more fuel when you back off or are changing down. Tuning principals remain the same regardless of whether it's got a carby or efi.
Outstanding HDF Member
Joined: Jun 2007
Posts: 2,687
Likes: 6
From: Kalaui Kona HI
RE: Decel Popping...What exactly is the problem with it?
I have had my bike on the dyno more times than I want to admit to tune out the decel. It happens in all pipes.Some mute the decel better than others.The stock pipes have it also you justdon't hear it. Your goal is to ensure the A/F numbers allow the bike to run cool as to not harm the engine.
Road Master
Joined: Oct 2006
Posts: 894
Likes: 1
From: Northport, AL
RE: Decel Popping...What exactly is the problem with it?
Decel Popping 101
Either (1) air is entering the exhaust system or (2) you're out of tuneon deceleration.
(1) On deceleration there is actually a momentary vacuum in your exhaust pipes after each cylinder fires. This vacuum helps extract the exhaust gasses of the next cylinder when it fires. That's why 2 into 1 exhaust systems are the most efficient. Even the tiniestleak in the gaskets of an exhaust system will suck in fresh air which will combine with the hot gasses containing the smallest traces of unburned fuel and immediately explode. Fix: Always use new crush gaskets on header installation and use new clamps & sealer on slip-on installation. Re-torque bolts after a few hours use. Short pipes are problematic, see #2.
(2) You can have a terriffic tune on your bike for performance but it pops on decel. The fix would be to richen up the mix on decel to the point that it's too rich to explode. If you have a tach, note the RPM range where (on deceleration) itpops. Go to your tuning software & richen up the VE values (both cylinders) at zero percent throttle for the approximate RPM range that you noted the popping. I prefer to increase them one unit at the time & try it. This can take several attempts,each time getting better.
GPM
Either (1) air is entering the exhaust system or (2) you're out of tuneon deceleration.
(1) On deceleration there is actually a momentary vacuum in your exhaust pipes after each cylinder fires. This vacuum helps extract the exhaust gasses of the next cylinder when it fires. That's why 2 into 1 exhaust systems are the most efficient. Even the tiniestleak in the gaskets of an exhaust system will suck in fresh air which will combine with the hot gasses containing the smallest traces of unburned fuel and immediately explode. Fix: Always use new crush gaskets on header installation and use new clamps & sealer on slip-on installation. Re-torque bolts after a few hours use. Short pipes are problematic, see #2.
(2) You can have a terriffic tune on your bike for performance but it pops on decel. The fix would be to richen up the mix on decel to the point that it's too rich to explode. If you have a tach, note the RPM range where (on deceleration) itpops. Go to your tuning software & richen up the VE values (both cylinders) at zero percent throttle for the approximate RPM range that you noted the popping. I prefer to increase them one unit at the time & try it. This can take several attempts,each time getting better.
GPM
Advanced
Joined: Dec 2007
Posts: 71
Likes: 0
From: Burnley UK
RE: Decel Popping...What exactly is the problem with it?
Hello i had the same problem with the same pipes.Re tighten the exhaust head bolts.And put in the quite baffles.It worked for me.I also run with Arlen Ness big shot Adjustable Fuel Injection Tuner.And Arlen Ness big mouth air cleaner.
Road Master
Joined: Nov 2006
Posts: 1,164
Likes: 401
From: Port Coquitlam B.C.
RE: Decel Popping...What exactly is the problem with it?
ORIGINAL: domenicp7
The stock pipes have it also you justdon't hear it.
The stock pipes have it also you justdon't hear it.
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Tourer
Joined: Mar 2008
Posts: 250
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From: SouthWest Iowa
RE: Decel Popping...What exactly is the problem with it?
Thanks for the info. Like I said, Its not near enough to be annoying for me but I really wanted to know what it ws since I see so much mention of it. SO, I am not touching it but I will make sure everything is tight.
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Joined: Jun 2006
Posts: 3,572
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From: Templeton California
RE: Decel Popping...What exactly is the problem with it?
Light poping is normal and harmless however loud backfiring is not and aside from being annoying and sounding like crap can actually blow a hole in your piston.