Fat boy decel
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Joined: Feb 2009
Posts: 90
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From: South Carolina
Fat boy decel
Need some opinions.. have V&H slip-ons ont the fatboy (carbed) and like the sound ok, but seem to get a muffled backfire on decel. It mainly happens in mountain riding when using the engine to help brake. I have been told several times from people behind me it sounds really bad. I did not do the stage 1 kit and curious if that would help? I guess the other option to change to full exhuast and stage 1 but budget is tight.
Several people have said something on rides so has anyone had the same experience?
Several people have said something on rides so has anyone had the same experience?
Tourer
Joined: Feb 2009
Posts: 362
Likes: 1
From: New York
I have to disagree with this post. I say the bike is running lean. Idle mixture screw to the max if necessary or one up on the pilot if that's not enough. Oh and yes, first double check exhaust bolts for tightness like above post
Last edited by BigJoeNY; Aug 3, 2009 at 12:36 PM.
Road Master
Joined: Apr 2009
Posts: 750
Likes: 1
my bike does the same thing. My buddies bike as well. I tend to think the bike is running a bit rich and the crackle noise is unspent fuel that detonates in the exhaust. I cant prove this but its just an opinion. I have the stage one on my bike as well. I am gonna get the bike tuned as soon as i can come p with the cash just for that. I could be wrong like i said just my 2 Cents 
Club Member
Joined: Aug 2007
Posts: 10,393
Likes: 2,060
From: N. Atlanta Burbs
It's called exhaust reverberation. During decel your exhaust system will suck in cool air and mix with the unburned mixture in your pipes. It will be ignited as the exhaust valve opens and boom. Decel pop. It can be corrected easier with a richer mixture than lean making it too rich to burn while in the pipes.
This is more common with open or drag pipes than with other types. It will also happen when you use slip on mufflers with large baffles and the stock head pipes that contain a stock crossover pipe.
Suggestions to cure this with a carborated bike is to go up 3 sizes on your metering jets and test. For EFI systems you can simply add fuel to your map process at 0 throttle.
This is more common with open or drag pipes than with other types. It will also happen when you use slip on mufflers with large baffles and the stock head pipes that contain a stock crossover pipe.
Suggestions to cure this with a carborated bike is to go up 3 sizes on your metering jets and test. For EFI systems you can simply add fuel to your map process at 0 throttle.
Tourer
Joined: Feb 2009
Posts: 362
Likes: 1
From: New York
Yikes... 
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Club Member
Joined: Aug 2007
Posts: 10,393
Likes: 2,060
From: N. Atlanta Burbs
Yeah, I freaked too when I heard this from a tuner but he swears by it. Says the upsize really isn't that much. Sold my carb bike years ago running like a spanked monkey.
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Ultimate HDF Member
Joined: Oct 2007
Posts: 5,257
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From: Leander Texas
here is a good place to start. read and learn.
http://www.harley-performance.com/index.html
Last edited by tk353; Aug 3, 2009 at 11:01 PM.