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Old 06-07-2010, 09:28 PM   #1 (permalink)
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Exhaust 'popping' on deceleration

I just picked up my Fuel injected 2001 Road King and I've got a question.

On downshifting and deceleration, I'm getting a lot of popping through the exhaust pipes. The PO, who was the second owner, said the first owner put a set of pipes on it, but thought it was otherwise completely stock.

My question is is this typical of this bike (I just moved up from a 1994 Sportster), or is there something I need to look at?

Thanks.
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Old 06-07-2010, 09:55 PM   #2 (permalink)
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Here is one of quite a few on this subject.
Do you have any fuel control system on the bike?
http://www.v-twinforum.com/forums/ha...decel-pop.html
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Old 06-07-2010, 10:22 PM   #3 (permalink)
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Without a add on fuel controller, it will pop on decel. They run lean. Get a good air cleaner and a fuel controller, and this will be reduced, possibly eliminated, depending on your exhaust.
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Old 06-07-2010, 11:13 PM   #4 (permalink)
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I like that noise. We ride Harleys, we really shouldn't be complaining about noise. Riching it up may get rid of it.
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Old 06-07-2010, 11:18 PM   #5 (permalink)
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This is from Mikuni's site:

It is normal for many high performance exhaust systems to moderately backfire or pop when the throttle is closed from mid-to-high rpm. In fact, one should expect a well-tuned high performance engine to "pop" and "crackle" when the throttle is closed at high rpm.

The popping is a result of the air/fuel mixture becoming very lean when the throttle is closed and the engine is rotating well above idle speed. It is also necessary that the exhaust system have rather open mufflers.

Why This (normally) Happens:

1) When the throttle valve is in the idle position, fuel does not flow out of the main system (needle, needle jet, main jet). Fuel is only delivered to the engine by the pilot (idle) system.
2) The combined effect of the closed throttle and elevated engine rpm is to create a fairly strong vacuum in the intake manifold. This vacuum, in turn, causes a high air flow rate through the small gap formed by the throttle valve and carburetor throat.
3) Under these conditions the pilot (idle) system cannot deliver enough fuel to create a normal, combustible air/fuel ratio. The mixture becomes too lean to burn reliably in the combustion chamber. It gets sent into the exhaust system unburned and collects there.
4) When the odd firing of the lean mixture does occur, it is sent, still burning, into the exhaust system where it sometimes ignites the raw mixture that has collected ---- the exhaust then pops or backfires.
5) Completely stock Harleys do not do this until open-end mufflers, such as the popular Screamin' Eagle slip-ons, are installed. The exhaust must be both free-flowing and have an open exit for the popping to occur.
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Old 06-08-2010, 07:06 AM   #6 (permalink)
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Could be an exhaust leak as well...........
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Old 06-08-2010, 09:59 AM   #7 (permalink)
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Originally Posted by SAFXDL View Post
Could be an exhaust leak as well...........
Most likely not as it would take a very loose set of nuts to generate that and you could here the telltale "tat tat' if you listen for it from the head.
Those compliant exhaust gaskets can handle lots of torque variance.
Just do a quick check on em when cold.
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Old 06-08-2010, 12:22 PM   #8 (permalink)
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Or your intake seals..........Also check the joints on your slipons for puffs of air.
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Last edited by SAFXDL; 06-08-2010 at 12:30 PM.
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Old 06-08-2010, 01:21 PM   #9 (permalink)
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Did they put on a new breather when they put the new pipes on. Sounds like all it needs is to be remapped.
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Old 06-09-2010, 03:51 PM   #10 (permalink)
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I agree with FLHT. Take it to a bike shop you can trust, and have them check the set up, it probably does need remapped.
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Old 06-09-2010, 08:33 PM   #11 (permalink)
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Al is right it could be leaks.
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Helmets are like rubbers you know you should wear one, but its so much better when you don't.-Me
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Old 06-09-2010, 09:35 PM   #12 (permalink)
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Quote:
Originally Posted by TheNowhereman View Post
This is from Mikuni's site:

It is normal for many high performance exhaust systems to moderately backfire or pop when the throttle is closed from mid-to-high rpm. In fact, one should expect a well-tuned high performance engine to "pop" and "crackle" when the throttle is closed at high rpm.

The popping is a result of the air/fuel mixture becoming very lean when the throttle is closed and the engine is rotating well above idle speed. It is also necessary that the exhaust system have rather open mufflers.

Why This (normally) Happens:

1) When the throttle valve is in the idle position, fuel does not flow out of the main system (needle, needle jet, main jet). Fuel is only delivered to the engine by the pilot (idle) system.
2) The combined effect of the closed throttle and elevated engine rpm is to create a fairly strong vacuum in the intake manifold. This vacuum, in turn, causes a high air flow rate through the small gap formed by the throttle valve and carburetor throat.
3) Under these conditions the pilot (idle) system cannot deliver enough fuel to create a normal, combustible air/fuel ratio. The mixture becomes too lean to burn reliably in the combustion chamber. It gets sent into the exhaust system unburned and collects there.
4) When the odd firing of the lean mixture does occur, it is sent, still burning, into the exhaust system where it sometimes ignites the raw mixture that has collected ---- the exhaust then pops or backfires.
5) Completely stock Harleys do not do this until open-end mufflers, such as the popular Screamin' Eagle slip-ons, are installed. The exhaust must be both free-flowing and have an open exit for the popping to occur.

good stuff but his bike is FI.
OP'er
Answer to your question it's normal for your set up. open air cleaner and free flowing pipes. if you have the stock cross over head pipes it even compounds the problem. left side sucks back air into the exhaust making it even leaner then the condition created with the A/C and pipes.
it can be tuned out with the right tuner and the right person tuning it.

as stated intake leak will cause this also as well as the mufflers leaking where they clamp on the head pipes.
my guess is they are fine...your just lean as he**
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Last edited by strokerjlk; 06-09-2010 at 09:48 PM.
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Old 06-09-2010, 11:35 PM   #13 (permalink)
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I know its FI but the physics are just the same.
Too lean down low; shut down the throttle..... backfire
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Old 08-30-2014, 09:05 PM   #14 (permalink)
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Hello this may not be the correct location for this post if so I apologize. I am having more exhaust sound coming out of the right exhaust pipe than the left. 2003 FLHTCUI stage 1 everything else stock. Lately sounding louder from the right then the left. The crossover pipe is stock as well. I am not complaining about the louder pipe just wondering why one over the other. Thank you for your response.
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Old 09-06-2014, 07:27 PM   #15 (permalink)
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Quote:
Originally Posted by Djfinster View Post
Hello this may not be the correct location for this post if so I apologize. I am having more exhaust sound coming out of the right exhaust pipe than the left. 2003 FLHTCUI stage 1 everything else stock. Lately sounding louder from the right then the left. The crossover pipe is stock as well. I am not complaining about the louder pipe just wondering why one over the other. Thank you for your response.
Look at the crossover pipe... see how it's flattened? Your right side is handling most of the exhaust, that's the way it is stock.
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