 Popping on deceleration
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OP
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I noticed that Pat with his new mikunis explained how he had some popping on deceleration. Now I only recently adjusted my air pilot screws from 2 3/4's to 2 1/2 and have noticed whilst I have fixed the slight hesitation when taking off from idle and she now has better acceleration, there is just a little bit of popping when decelerating. Can anyone tell me if this is a problem and if so, what should I do about it? thanks guys
Staintune Pipes, K&N Pods, 45 pilots, TBS needles and 145 mains.
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Re: Popping on deceleration
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It's not really a problem if it's minor and doesn't bother you too much. It can mean that you are running a little lean as well, so check your plugs. Sometimes you have to trade a little popping for max performance.
Not you fat Jesus!
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Re: Popping on deceleration
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Joined: Sep 2006
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Learned Hand
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Learned Hand
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Quote:
It's not really a problem if it's minor and doesn't bother you too much. It can mean that you are running a little lean as well, so check your plugs. Sometimes you have to trade a little popping for max performance.
And if it continues to bother you - Just don't slow down 
2004 Triumph Speedmaster (J Lo) 2006 Yamaha Stratoliner (Adele)
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Re: Popping on deceleration
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Joined: Jul 2006
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Learned Hand
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Learned Hand
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You can try going up to a 45 pilots. Also check for any exhaust leaks.
2002 Bandit 1200/ GSXR cams/ 1277 BB Kit/ Holeshot header and can/ 38mm flatslides/ a good head/lotsa hp/lotsa tq- lots of rear tires...
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Re: Popping on deceleration
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Joined: Dec 2006
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Oil Expert
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OP
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thanks for that. No it doesn't bother me at all really, I just wanted to know what it meant. Funny though, when the mixter screw was a 2 3/4's it smelt a little bit fuelly when idling she wasn't quite running right. I adjusted to 2 1/2 like I said and now may bit a bit lean. Now having spoken to you, I think she might be about right. Regards the plugs, I had looked at them a couple of weeks back and they were definitely on the dirty side so it all adds up to be fine I reckon. I'll check the plugs in a couple of weeks and wouldn't be surprised if they were much lighter.
Staintune Pipes, K&N Pods, 45 pilots, TBS needles and 145 mains.
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Re: Popping on deceleration
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Joined: Jan 2005
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Should be Riding
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Should be Riding
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With the pipes I have, that popping can kinda get loud. I like it when I am in a tunnel, especially if there is someone next to me on their cell phone.
Soren
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Re: Popping on deceleration
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Joined: Jan 2005
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Quote:
With the pipes I have, that popping can kinda get loud. I like it when I am in a tunnel, especially if there is someone next to me on their cell phone.
Soren
I have the same Soren. It is cool sometimes. I am going to re-pack my very open baffles to see what effect, if any, that has on the popping.
In Between the Dark and the Light..
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Re: Popping on deceleration
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Worn Saddle
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Worn Saddle
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Ryan and Staffo,
I got rid of 90% of the popping today. Doh! My right hand carb manifold's squirrel condom was pretty loose and was leaking I guess. I just jump-hosed the manifolds with 3/32" tubing and bingo!
Ryan, I know you have BGs nice SS manifolds so not sure what to do with yours - maybe turn the one air screw out a pubimeter? - I remember they are only at about 1/8 turn already and are very touchy.
A word to the wise is not necessary. It is the stupid ones who need the advice.
Pat
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Re: Popping on deceleration
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Just want to make sure I got this straight. Popping on decel is usually a sign of being too lean?
Put in TBS needles yesterday. Got the extra punch in the midrange as advertised. I also got more popping on decel, which confuses my little brain since I just made things richer. AI is out.
My set up:
06 TBA: Thunderbikes, 42, 132, AI out, TBS, top snork out.
Thanks.
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Re: Popping on deceleration
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Joined: Jan 2005
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Oil Expert
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Oil Expert
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Quote:
Ryan and Staffo,
I got rid of 90% of the popping today. Doh! My right hand carb manifold's squirrel condom was pretty loose and was leaking I guess. I just jump-hosed the manifolds with 3/32" tubing and bingo!
Ryan, I know you have BGs nice SS manifolds so not sure what to do with yours - maybe turn the one air screw out a pubimeter? - I remember they are only at about 1/8 turn already and are very touchy.
Extremely touchy!
In Between the Dark and the Light..
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Re: Popping on deceleration
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Joined: Jan 2005
Posts: 2,297
Oil Expert
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Oil Expert
Joined: Jan 2005
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Quote:
Just want to make sure I got this straight. Popping on decel is usually a sign of being too lean?
Put in TBS needles yesterday. Got the extra punch in the midrange as advertised. I also got more popping on decel, which confuses my little brain since I just made things richer. AI is out.
My set up:
06 TBA: Thunderbikes, 42, 132, AI out, TBS, top snork out.
Thanks.
Did you shim the TBS needles?
In Between the Dark and the Light..
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Re: Popping on deceleration
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Joined: Sep 2006
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Adjunct
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Adjunct
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Quote:
Quote:
Just want to make sure I got this straight. Popping on decel is usually a sign of being too lean?
Put in TBS needles yesterday. Got the extra punch in the midrange as advertised. I also got more popping on decel, which confuses my little brain since I just made things richer. AI is out.
My set up:
06 TBA: Thunderbikes, 42, 132, AI out, TBS, top snork out.
Thanks.
Did you shim the TBS needles?
No, just dropped em in.
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Re: Popping on deceleration
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Joined: Mar 2007
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Have you removed AI system?
Air injection produces lot of popping also with rich carburetion.
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Re: Popping on deceleration
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Joined: Sep 2006
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Adjunct
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Adjunct
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Quote:
Have you removed AI system?
Air injection produces lot of popping also with rich carburetion.
yes, AI is out.
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Re: Popping on deceleration
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Joined: Jun 2006
Posts: 1,138
Learned Hand
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Learned Hand
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John,
Anytime you mess with the carbs, you should re-balance the carbs. There are two on Brents site and there is a link in the tech vault on how to make your own.
I went with Brents cheap on and it works great. You will not believe the difference balanced carbs make not saying it will get rid of the popping on decel.
I actual think it is cool I gave up trying to get rid of it you can but you end up with the flat spot on the low or mid range. I have my screws three turns out and he runs like a raped ape.
John 06 America Mulberry\Silver
"Seemed Like A Good Idea At The Time"
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Re: Popping on deceleration
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Joined: Jul 2006
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Learned Hand
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Learned Hand
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Quote:
Just want to make sure I got this straight. Popping on decel is usually a sign of being too lean?
Put in TBS needles yesterday. Got the extra punch in the midrange as advertised. I also got more popping on decel, which confuses my little brain since I just made things richer.
You made it richer in the midrange. The needle does not affect your idle. The needle enters the fuel circuit at about 1/4 throttle and is out of the circuit at 3/4 throttle. Try going to a 45 pilot. Also check the vaccuum plugs, i.e. squirrel condoms, and look for exhaust leaks.
this is a good source for carbs and how they work...http://www.motorcyclecarbs.com/carbs101.pdf
2002 Bandit 1200/ GSXR cams/ 1277 BB Kit/ Holeshot header and can/ 38mm flatslides/ a good head/lotsa hp/lotsa tq- lots of rear tires...
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Re: Popping on deceleration
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Thanks guitarted. That helps.
So, to make sure I have it straight: With 132 mains and 42 pilots, I could be lean in the pilot circuit, good in the midrange and a bit rich at full throttle?
Thanks.
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Re: Popping on deceleration
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Joined: Jan 2006
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Loquacious
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Loquacious
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ok here we go again...a PROPERLY tuned motor with high performance pipes WILL POP in DECEL....
From the mikuni site....
Note: 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.
One thing that should be pointed out is that while the throttle may be
closed, leaning up the mixture, and it may take several revolutions of
the engine to build up a burnable mixture in the pipe, the engine will
still be running at a high enough RPM for the ignition advance curve to
be advancing the ignition. So, if you have an ignition system that
fires a waste spark, it's going to fire that spark during the valve
overlap period on one of your four cylinders, and that's enough to make
the exhaust backfire.
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.
your engine, rather because it is an indication of lean and running so
can burn your exhaust valves everyone thinks it to be a bad thing.
Tuning your bike richer means an excess of fuel and very little to no
oxygen. Thus the unburned fuel passes through the pipe without ever
igniting. So you can think of the popping as a sort of environmental
control on your bike, combusting excess fuel that would have otherwise
not gotten burned.
THE VOICE OF REASON
per: Stewart
AF&AM/Shriner/Scoutmaster
130/45 TBS 2shim SS Uni 18/42
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Re: Popping on deceleration
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Joined: Jul 2006
Posts: 1,337
Learned Hand
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Learned Hand
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Quote:
Thanks guitarted. That helps.
So, to make sure I have it straight: With 132 mains and 42 pilots, I could be lean in the pilot circuit, good in the midrange and a bit rich at full throttle?
Thanks.
No. I was trying to make the point that you didn't affect the idle circuit when you changed the needle.
2002 Bandit 1200/ GSXR cams/ 1277 BB Kit/ Holeshot header and can/ 38mm flatslides/ a good head/lotsa hp/lotsa tq- lots of rear tires...
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Re: Popping on deceleration
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Joined: Jan 2005
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Should be Riding
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Should be Riding
Joined: Jan 2005
Posts: 12,164 Likes: 1 |
Hey Rob, thanks for posting that. I did no know, now I do. Very Cool!
Soren
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Re: Popping on deceleration
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Joined: Dec 2006
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OP
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now just remember I'm new at this thing also but maybe cos as the popping is happening with no throttle open as you are decelerating, you are only lean due to you air idle screw needing adjustment out. From what I've read, the tbs (which I have also) are effective midrange therefore having no impact on deceleration. Just how I see it and am happy if someone tells me I'm talking crap.
Staintune Pipes, K&N Pods, 45 pilots, TBS needles and 145 mains.
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Re: Popping on deceleration
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Oil Expert
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Rob, very good stuff. Pop goes the blue Trump through Central Florida!
In Between the Dark and the Light..
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Re: Popping on deceleration
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Joined: Jan 2006
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Loquacious
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Loquacious
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No Problem....just remember if you DO get rid of it all( the poppin)...(and you can)your running RICH on the low end...
THE VOICE OF REASON
per: Stewart
AF&AM/Shriner/Scoutmaster
130/45 TBS 2shim SS Uni 18/42
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Re: Popping on deceleration
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Joined: Dec 2006
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Oil Expert
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OP
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Rob, I reckon you are right on that one. Mine only pops (so to speak) in only a minor way and my bike has never ridden so well. I think it's spot on, so it's nice to know what these little symptoms mean so we can get optimum performance and economy.
Staintune Pipes, K&N Pods, 45 pilots, TBS needles and 145 mains.
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Re: Popping on deceleration
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Joined: Jan 2005
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Oil Expert
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Oil Expert
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Quote:
Rob, I reckon you are right on that one. Mine only pops (so to speak) in only a minor way and my bike has never ridden so well. I think it's spot on, so it's nice to know what these little symptoms mean so we can get optimum performance and economy.
I know what you mean. My bike pops quite a bit no matter the RPM, but I have tons of torque and power across the throttle. Perhaps, a richer needle could eliminate some of the popping at the lower end, but I am not sure of making that change. With the carbs and 904 kit, it takes me a good 3 minutes or so to warm up the motor.
In Between the Dark and the Light..
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Re: Popping on deceleration
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Joined: Jan 2005
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Big Bore
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Big Bore
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Mine is popping also so I've given up trying to remove it. Now I just enjoy! 3 minutes! I guess we know who's getting up earlier than everyone else in GA, eh?
"Never underestimate the power of human stupidity" - Robert Heinlein
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Re: Popping on deceleration
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Joined: Feb 2007
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Fe Butt
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Fe Butt
Joined: Feb 2007
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My SM doesn't pop much at all. Its all in the idle mixture screws and pilot jets. It does pop a little every once in awhile but under normal easy conditions it doesn't.Freak...155 main 48 pilot ...AI removed....gutted stock pipes...dyno at 13ppm pretty much perfect air fuel mixture. took some playing to get it there.
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Popping on deceleration
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Big Bore
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Big Bore
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Every big bore I've seen burbles a bit no matter what you do with jets or needles. It's no big deal.
"Never underestimate the power of human stupidity" - Robert Heinlein
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Re: Popping on deceleration
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Joined: Jan 2005
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Worn Saddle
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Worn Saddle
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Quote:
Every big bore I've seen burbles a bit no matter what you do with jets or needles. It's no big deal.
Big 10-4 on that statement Phil. 
A word to the wise is not necessary. It is the stupid ones who need the advice.
Pat
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Re: Popping on deceleration
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Joined: Jan 2006
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Loquacious
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Loquacious
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Quote:
Quote:
Every big bore I've seen burbles a bit no matter what you do with jets or needles. It's no big deal.
Big 10-4 on that statement Phil.
As it should, if it's properly tuned...if you did manage to get rid of it all (according to Mikuni) you would have a overly rich pilot circuit...
THE VOICE OF REASON
per: Stewart
AF&AM/Shriner/Scoutmaster
130/45 TBS 2shim SS Uni 18/42
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Re: Popping on deceleration
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Joined: Aug 2005
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Loquacious
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Loquacious
Joined: Aug 2005
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Quote:
I also got more popping on decel, which confuses my little brain since I just made things richer.
I ended up turning out my mixture screws out to 3 1/2 turns out. 90% gone
Erwin
05 America
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Re: Popping on deceleration
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Oil Expert
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Oil Expert
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Quote:
Every big bore I've seen burbles a bit no matter what you do with jets or needles. It's no big deal.
Yep, our rather open pipes are a big factor. POW-POW!
In Between the Dark and the Light..
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Re: Popping on deceleration
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Joined: Feb 2007
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Fe Butt
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Fe Butt
Joined: Feb 2007
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like I said mine does just a little but 90% or better gone. it does rumble a little on deceleration. But not that popping sound. According to my dyno runs it is dialed in as close to perfect as you are gonna get. small dip in mid range but that is pretty much normal with open pipes. air fuel is at 13 pretty much across the board.
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Popping on deceleration
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Big Bore
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Big Bore
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Try dropping in needles from a ThunderBird Sport (TBS). You will probably lose that dip.
"Never underestimate the power of human stupidity" - Robert Heinlein
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Re: Popping on deceleration
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Joined: Feb 2007
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Fe Butt
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Fe Butt
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I was wondering about the needle changes. Do I need to shim them or anything? Or change jets again? Use different spring or diaphram?
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Popping on deceleration
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Joined: Jan 2005
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Big Bore
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Big Bore
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Nah, I would just do the needles first. No shim. The profile is not a whole lot different that the stocker but just different enough where a lot of people have reported losing that lag, including me.
"Never underestimate the power of human stupidity" - Robert Heinlein
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Re: Popping on deceleration
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Joined: Feb 2007
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Fe Butt
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Fe Butt
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Cool. Thanx for the info I'll give it a shot and let ya know what it does for us.
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Popping on deceleration
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Joined: Jan 2006
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Loquacious
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Loquacious
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TBS needles DEFINATELY helped my mid range flat spot (dip) just pull the old (stock) one out and drop in the TBS...you may need to adjust the air mix...but only slightly
THE VOICE OF REASON
per: Stewart
AF&AM/Shriner/Scoutmaster
130/45 TBS 2shim SS Uni 18/42
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Re: Popping on deceleration
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Joined: Feb 2007
Posts: 23,198 Likes: 56
Fe Butt
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Fe Butt
Joined: Feb 2007
Posts: 23,198 Likes: 56 |
1 other question what year Tbird?
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: Popping on deceleration
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Joined: Jan 2006
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Loquacious
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Loquacious
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never asked...just told the Stealer I needed TBS needles they ordered them ($14.00) droped them in...done
THE VOICE OF REASON
per: Stewart
AF&AM/Shriner/Scoutmaster
130/45 TBS 2shim SS Uni 18/42
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