Deceleration popping

[Spikes05]

Hey y'all I want to get straight on what causes deceleration popping. Some say it is a rich air fuel situation and others say that it is a lean air fuel situation. So which is it to rich or to lean?


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[bdm7250]

Popping on deceleration is caused by a LEAN condition. When you suddenly close the throttle, the incoming air is choked off and the closed throttle also causes the bike to return to idle on the very lean idle circuit. However, momentum of the bike is actually "driving" the engine in a sense, and that engine is still spinning at rpm that needs far more gas than the closed throttle position can provide. The engine is still spinning but the incoming fuel rate is very low, until just enough builds up in the combustion chamber to "fire" on the exhaust stroke of the engine.

 

[Spikes05]

Popping on deceleration is caused by a LEAN condition. When you suddenly close the throttle, the incoming air is choked off and the closed throttle also causes the bike to return to idle on the very lean idle circuit. However, momentum of the bike is actually "driving" the engine in a sense, and that engine is still spinning at rpm that needs far more gas than the closed throttle position can provide. The engine is still spinning but the incoming fuel rate is very low, until just enough builds up in the combustion chamber to "fire" on the exhaust stroke of the engine.

So would you increase the intermediate jet or the main jet or both


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[bdm7250]

So would you increase the intermediate jet or the main jet or both


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What have you done to your bike? Exhaust, cam, etc.?

 

[Spikes05]

What have you done to your bike? Exhaust, cam, etc.?

I changed the exhaust and the air cleaner. I used to have mean mothers and stock air cleaner and I installed hooker headers Darkside big radius pipes and an S&S Dual Runner


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[Spikes05]

I have had the V&H Big Radius in the past and I installed BCT baffles and that solved the problem. However the Darkside B&R is 2.5" O.D. and 2.25 I.D. and big city thunder baffles only make baffles for 2.25 O.D. So I am trying to fail in the jets and air fuel mixture.


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[BWG56]

Try this

 

[Spikes05]

Try .32 intermediate and .78 main I also had mean mothers and those were the jets recommended and I put a paul yaffee phantom pipe on and spike air cleaner and they also were the perfect match , with the dual runner you may possibly need .33 int also be sure and adjust the carb very simple process only takes a few minutes

Okay thanks I have .032 and a .076 and I was wondering if I should try the .033 and .078 combo.


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[BWG56]

Okay thanks I have .032 and a .076 and I was wondering if I should try the .033 and .078 combo.


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Before you do that, did you try removing the Auxiliary bowl vent and readjusting the carb? look at the PDF, its #14
With aftermarket air filters, this should be removed

 

[BWG56]

What pipes and air cleaner are you running?

 

[Spikes05]

Before you do that, did you try removing the Auxiliary bowl vent and readjusting the carb? look at the PDF, its #14
With aftermarket air filters, this should be removed

Why would I do that I am running a S&S Dual Runner and it has the bowl vent built into the assembly. Does it need more venting than that?


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[Spikes05]

What pipes and air cleaner are you running?

Hooker Headers Darkside Big Radius


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[Spikes05]

Did it feel like it was stumbling kinda like it was beginning to run out of gas but only off and on while you were cruising at those speeds?


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[BWG56]

Why would I do that I am running a S&S Dual Runner and it has the bowl vent built into the assembly. Does it need more venting than that?
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I am running the BR and the dual runner also with the vent removed because that's what they recommend you do, I tried 32 and 78 and at while cruising at 50-55 it would sneeze thru the carb, per their (S&S) carb adjustment guide, they recommended to bump up the inter a size, that's why I'm running 33 and 78 now without any hickups.
You ask why would you do that? because its not running right now. Follow the istructions they have on the PDF, what you have to remember is no 2 bikes are a like because of tolerances, think about it, from .032 to .033 is .001. What if the tolerance is +/-.0005, you could have a .032 at .0315 and a ,033 at .0335, that's .002 difference. Is that going to make a difference? You bet it is.

 

[Spikes05]

I am running the BR and the dual runner also with the vent removed because that's what they recommend you do, I tried 32 and 78 and at while cruising at 50-55 it would sneeze thru the carb, per their (S&S) carb adjustment guide, they recommended to bump up the inter a size, that's why I'm running 33 and 78 now without any hickups.
You ask why would you do that? because its not running right now. Follow the istructions they have on the PDF, what you have to remember is no 2 bikes are a like because of tolerances, think about it, from .032 to .033 is .001. What if the tolerance is +/-.0005, you could have a .032 at .0315 and a ,033 at .0335, that's .002 difference. Is that going to make a difference? You bet it is.

Okay thanks I will set it up today with a .033 intermediate jet and a .078 main jet and I will pull the auxiliary bowl vent. I will let you know what happens tonight. Thanks again


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[BWG56]

Okay thanks I will set it up today with a .033 intermediate jet and a .078 main jet and I will pull the auxiliary bowl vent. I will let you know what happens tonight. Thanks again


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Please do, we like to hear a happy ending

Just try removing the vent first before you bump up the jet

 

[bdm7250]

Okay thanks I will set it up today with a .033 intermediate jet and a .078 main jet and I will pull the auxiliary bowl vent. I will let you know what happens tonight. Thanks again


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Let us know how you make out.

 

[Spikes05]

He said he would so back off there chucky!

Hey guys it's awesome!!! I put the .033 in and removed the auxiliary bowl vent plug and it runs like a raped ape!!! As for the deceleration popping it's gone it's more like a gurgle or growling I would say a growling and its not that bad of a growling so thanks to all of you for your support and help I really appreciate everything that you have done for me.


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[Spikes05]

Great news! Did you also dial in the carb?

Yes I tuned the carb and put it through all the tests and It is perfect!!!


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[bdm7250]

Hey guys it's awesome!!! I put the .033 in and removed the auxiliary bowl vent plug and it runs like a raped ape!!! As for the deceleration popping it's gone it's more like a gurgle or growling I would say a growling and its not that bad of a growling so thanks to all of you for your support and help I really appreciate everything that you have done for me.


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Thanks for the update..