decel pops and burbles - good or bad?
Elite HDF Member
Joined: Aug 2008
Posts: 4,133
Likes: 125
From: Japan
Unspent fuel being blown into free-flowing pipes where it is mixed with more air and heat, causing trace amounts of that fuel to combust there; is the phenomenon known as "decel pop". Richening the AFR will not help. This only pours more fuel into the combustion chamber where more of the unspent fuel will be blown into the exhaust pipe, making the problem worse, if anything. Most tuners have a "decel cut" or "decel pop elimination" feature, which usually just cuts fuel between certain RPMs on decel. Sometimes it helps, sometimes not, but this still doesn't get to the root of the problem. The fuel must be burned more completely before being dumped out the exhaust port. Only adding timing (advancing the timing of the ignition spark) most effectively eliminates decel pop. This is also part of tuning a motor to run its best. Most people only look at AFR because it's easiest to adjust and understand, but it's only half of the equation...
Last edited by HoggyMtnBreakdown; Oct 4, 2017 at 06:28 PM.
Banned
Joined: Jan 2012
Posts: 3,098
Likes: 474
From: Location location.
Everyone is commenting on his decel burble here and decel burble is a thing I like as it's running leaner because YOU'VE CUT THE THROTTLE but this guys bike if I read it correctly it's backfiring on the up shift FFS !!
Seriously mate get it seen to ,that could be way way lean, a leak somewhere or a timing thing .
Not being there also is a pisser as how you describe the problem may be understood differently to those reading.
Yea I just reread it get it seen to straight away!
Do not ride it !
Seriously mate get it seen to ,that could be way way lean, a leak somewhere or a timing thing .
Not being there also is a pisser as how you describe the problem may be understood differently to those reading.
Yea I just reread it get it seen to straight away!
Do not ride it !
Last edited by badcooky; Oct 4, 2017 at 09:17 PM.
Club Member
Joined: Mar 2009
Posts: 66,128
Likes: 51,461
From: Niles Canyon Ca.
No think about it you change the box to a non factory or Screaming Chicken the power train warranty gone on a 17 or newer bike, the VIN will be red flagged in the moco database.
Cruiser
Joined: Aug 2017
Posts: 214
Likes: 33
From: Colorado
While I'm no expert tuner, I've ridden and worked on all manner of motorcycles for over 30 years with a fair number of those road-racing.
As others have already said, GET IT TUNED! Without riding it and hearing it for myself, its too hard to diagnose what the problem may be.
Full-pipes almost always require a re-tune. Its typically only when you put slip-ons on that it may not be necessary. But anytime you increase either intake or exhaust you need to adjust the other.
I've ALWAYS made it part of the "exhaust" package for any of my bikes that if I change the pipes/can I'm getting a Power Commander/rejet or a re-tune to ensure the bike is running absolutely correct. I know alot of people that just spend the money on a pipe and wonder why they are getting more popping or backfires...
In some cases if it runs too lean you can burn valves or damage your engine...
As others have already said, GET IT TUNED! Without riding it and hearing it for myself, its too hard to diagnose what the problem may be.
Full-pipes almost always require a re-tune. Its typically only when you put slip-ons on that it may not be necessary. But anytime you increase either intake or exhaust you need to adjust the other.
I've ALWAYS made it part of the "exhaust" package for any of my bikes that if I change the pipes/can I'm getting a Power Commander/rejet or a re-tune to ensure the bike is running absolutely correct. I know alot of people that just spend the money on a pipe and wonder why they are getting more popping or backfires...
In some cases if it runs too lean you can burn valves or damage your engine...
Cruiser
Joined: Jun 2016
Posts: 157
Likes: 42
From: Wayne, NJ
FP-3 FuelPaks are sold at many Harley dealers in the parts department. Many even recommend them when changing pipes. It stores your old ECM program so you can always revert back to it if you need to if there is a warranty issue with a repair.
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
7 Times Harley-Davidson Chucked Tradition Out the Window
Verdad Gallardo
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Verdad Gallardo
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
Cruiser
Joined: Nov 2016
Posts: 227
Likes: 29
From: Atlanta
Everyone is commenting on his decel burble here and decel burble is a thing I like as it's running leaner because YOU'VE CUT THE THROTTLE but this guys bike if I read it correctly it's backfiring on the up shift FFS !!
Seriously mate get it seen to ,that could be way way lean, a leak somewhere or a timing thing .
Not being there also is a pisser as how you describe the problem may be understood differently to those reading.
Yea I just reread it get it seen to straight away!
Do not ride it !
Seriously mate get it seen to ,that could be way way lean, a leak somewhere or a timing thing .
Not being there also is a pisser as how you describe the problem may be understood differently to those reading.
Yea I just reread it get it seen to straight away!
Do not ride it !
+1...I initially commented earlier mentioning something about heat, primarily based on the OPs statement of the upshifting pops/backfires. Others have since contributed to this post and have disregard the OPs
"However, it is popping (more like a backfire sound) quite badly on upshifts as I roll off and squeeze the clutch, especially 1-2 and 2-3 gear shifts."
I'm also a bit perplexed on how the OP can be "OK" with the backfires/pops when shifting through 3 gears. That would irritate the crap out of me.
"However, it is popping (more like a backfire sound) quite badly on upshifts as I roll off and squeeze the clutch, especially 1-2 and 2-3 gear shifts."
I'm also a bit perplexed on how the OP can be "OK" with the backfires/pops when shifting through 3 gears. That would irritate the crap out of me.