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Oct 29, 2014 | 02:59 PM

#11

Prime Rib

Elite HDF Member

Joined: Oct 2013

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From: Citrus County, FL

I had terrible decel popping. It turned out that my older model Screaming Eagle slip ons (which have 3 small baffles instead of one large one) were missing a baffle in each muffler. After I put on a new set of Full Boar slip ons, there is no decel popping to be found.

This is on an EFI bike.

Oct 29, 2014 | 03:12 PM

#12

MSP Dan

Cruiser

Joined: Sep 2014

Posts: 151

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From: Twin Lakes WI

The same things apply to EFI bikes. At least on the MM bikes. I don't know whether it applies to Delphi bikes or not as I've never owned one. The typical "lean pop" tends to be somewhat muted and there will usually be a series of pops on decel. When it's an exhaust leak, it tends to be quite the bang and usually only one at a time.

On carbed and MM bikes (and again, maybe on Delphi bikes and maybe not) there is always unburned fuel in the exhaust. It doesn't pop because there isn't enough oxygen present to ignite.

Oct 29, 2014 | 06:07 PM

#13

br549A1

Outstanding HDF Member

Joined: Nov 2013

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Quote:

Originally Posted by tmanbuckhunter

Nothing wrong with decel pop. Some say it is caused by a lean condition when you have pop out of the pipes but I disagree, and so do several engine builders. Decel pop is caused when you have unburnt fuel get pushed out of the cylinder and into the exhaust, where you have a vaccum under decel allowing it to burn off in the exhaust. When you have a little bit of decel pop it usually means your carb/timing are just about spot on. I get more decel pop in the cold air. When I left Houston 2 or 3 weeks ago it was still warm and I didn't get much popping, but when I had my first run in Tallahassee it was about 48* or so... all motors love cool, dry air.

I disagree. There's two causes lean and rich. For a rich backfire his exhaust would be black all the time. Lean condition increases the exhaust gas temp which in turn causes the popping on decel. Is the bike coughing off idle or backfiring on decel? I would check the jet sizes and possibly go up one on the pilot depending on where you're at. I bet he's coughing off idle. Also what about exhaust? Straight pipes or slip ons?

Last edited by br549A1; Oct 29, 2014 at 06:23 PM.

Oct 29, 2014 | 08:42 PM

#14

imjwag

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From: Louisiana

'96 fxd

I just recently purchased this little dyna and noticed it had a random hic-up/spit/cough/whatever you call it when i would roll back into the throttle after deceleration and i was told that it sounded like the carb just needed a good cleaning. I removed the carb and disassembled it to find that the jets are standard as supposed to be, according to the service manual for it's year. - main j 170 and a 42 for the slow...I didn't find anything plugged up and for the most part was clean and in good working condition. I installed new intake manifold seals and new seal ring between carb and manifold.
It has khrome werks exhaust w/no baffles that I can tell and a high flow intake filter(don't know manufacturer),

Last edited by imjwag; Oct 29, 2014 at 08:52 PM.

Oct 29, 2014 | 08:57 PM

#15

br549A1

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You might need to install lollipops in the exhaust not sure, but you probably need a 45 or 46 pilot. Is the mixture screw cover drilled? Is the needle stock non adjustable or is it adjustable?

Oct 30, 2014 | 05:49 PM

#16

imjwag

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From: Louisiana

The mixture screw is accessible and the needle is adjustable

Oct 30, 2014 | 05:50 PM

#17

br549A1

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Quote:

Originally Posted by imjwag

The mixture screw is accessible and the needle is adjustable

try raising the needle by lowering the clip one notch. I still think you need a 45 pilot but see if that helps. It's quick to try. It should only effect mid but it did change my decel popping before I rejetted

I have an extra 45. PM me your name and address and I can mail it to you tomorrow. I bought it and ended up with two so it's yours if you need it.

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Last edited by br549A1; Oct 30, 2014 at 06:10 PM.

Oct 31, 2014 | 08:53 PM

#18

imjwag

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From: Louisiana

I appreciate the offer on the 45 but just so happened to have already picked up a few various sizes to have on hand when I start the tuning process....thanks again