Decel pop
- Thread starter COOPer
- Start date
What exhaust are you running? There are several things that cause that. Exhaust gasket leaking, baffles to short or non existence. Or it may be as simple as readjusting the carb.
I had that same thing when I bought my 03 chopper with shotgun Vance hines pipes. Installed 2 inch baffles and that took care of my problem. My off popping wasn't fuel related popping. If my acceleration pump adj. is off a bit, it will pop or backfire on off throttle. I first started with 4 inch baffles but that caused the rev limiter to kick in early.
Rather than upset the regulars around here with the long and drawn out theory; listen to the limiter kick in, noise gone, but by stopping here, I'll just use your quote, 'My bike runs great,' and suggest if you want to keep it running like that, I'll just say something about this, and that... someone once told me, "Takes a man to live with the pop.'
Mastiff Rider64
Well-Known Member
Well I think we have a reason it pops. lol. No baffles which those pipes I don't think were designed for baffles they are straight thru pipes like my Martin Brother Daisy cutters which I have on my 09 EFI Bulldog Bagger and guess what they pop on hard decels and hard accel. But no baffle or torque cones and with a straight thru pipe, 90 percent of the time when you decel hard its going to pop. lol
Jersey Big Mike
100K mile club
As someone once told me (on here I believe) when I had a similar issue.
It's a dog -- let it bark!
It's a dog -- let it bark!
Decel Disclaimer Theory:
I think you need a lot more of the gas element [pure oxygen] than fresh air that is about to heat up and det? The exhaust temp is slowing down. Fire off, boil stops, right? That's why they wrap the pipe to keep the hot air moving. Hot moves faster than cold, right? FI has an air induction system out of an exhaust port... fresh air to refire the unspent. Keep the cat hot to chemically neutralize the gas and such. It would more cool the cat on lift.
For what it's worth: had straight high pipes that reached to the rear wheel. Raw pipe. A hot spot was about 8-9" in from the end of the pipes. What are the odds that pop was the hotspot, and fired right there when air came in on lift adding oxygen. That's as far as that bubble went in and stopped. The constant is the push out, so how far could that bubble return up the pipe? About 9" where no other area has that blue burn to the raw metal.
Carb emissions evolution wise, there was a diaphragm that opened under throttle close. This opened an air channel cast into the carb body. It traveled up to the top of the carb's throttle slide where air was not under vacuum but to pull from a constant 14.7 pressure. When the piston created that vacuum on the down stroke, that gate being open, added air out that came out of the slow jet than fuel. Less fuel being pulled out of one of the jet circuits. Thus the better gas mileage, and customer complaint was twofold about a pop being eliminated.
Lift on the air chambered carb, there is less gas being pulled out of a jet circuit. Thus, there is no, to little explosions on the hang. What's there to fire but less, right? Do you agree smoke is constant are rings, and smoke on lift then clears are the guides? Then you have to agree that a tight guide still shows that [invisible smoke hang] is that gas hang you can't see on lift is the constant, agreed?
I more can look back at the evolution of the carb's design addressing a mandate to up the mileage on vehicles, where coincidence meets emissions, and if it resolved a customer complaint about a pop? It's not the more air fallacy, it's more, who entered the chamber sooner to fill the void, gas or air?
I think you need a lot more of the gas element [pure oxygen] than fresh air that is about to heat up and det? The exhaust temp is slowing down. Fire off, boil stops, right? That's why they wrap the pipe to keep the hot air moving. Hot moves faster than cold, right? FI has an air induction system out of an exhaust port... fresh air to refire the unspent. Keep the cat hot to chemically neutralize the gas and such. It would more cool the cat on lift.
For what it's worth: had straight high pipes that reached to the rear wheel. Raw pipe. A hot spot was about 8-9" in from the end of the pipes. What are the odds that pop was the hotspot, and fired right there when air came in on lift adding oxygen. That's as far as that bubble went in and stopped. The constant is the push out, so how far could that bubble return up the pipe? About 9" where no other area has that blue burn to the raw metal.
Carb emissions evolution wise, there was a diaphragm that opened under throttle close. This opened an air channel cast into the carb body. It traveled up to the top of the carb's throttle slide where air was not under vacuum but to pull from a constant 14.7 pressure. When the piston created that vacuum on the down stroke, that gate being open, added air out that came out of the slow jet than fuel. Less fuel being pulled out of one of the jet circuits. Thus the better gas mileage, and customer complaint was twofold about a pop being eliminated.
The gas is still pulled out of all 3 circuits. Gas is never shut off, just less off it [if no air induction system] is this style on the BD. The gas kind of stagnates in a way like if they were worn valve guides. In other words, when you lift off the throttle and coast, the gas keeps being sucked in and fired/not fired. When the throttle is applied, you see a puff of smoke come out of the exhaust and then clears. You never see it on lift with tight guilds, right? So that air just hangs in there and the flame front eventually fires the hang, you hear it pop in the pipe.
Lift on the air chambered carb, there is less gas being pulled out of a jet circuit. Thus, there is no, to little explosions on the hang. What's there to fire but less, right? Do you agree smoke is constant are rings, and smoke on lift then clears are the guides? Then you have to agree that a tight guide still shows that [invisible smoke hang] is that gas hang you can't see on lift is the constant, agreed?
Because, it's this side of the speed of light calculating, it's done before the other 3 strokes are doing their thing. And do you agree a computer bike mimics a carb; that it never shuts off on lift? Then hit the kill switch and get back to me about that fallacy that FI shuts off fuel on lift.
You mean the beauty of FI is that it can run up in elevation and adjust, where a carb has to be rejetted or runs too rich with less air? You mean that if a sensor fails, the ECU has a backup plan and the alpha number to calc off of is 14.7psi/760mmHg/1 atm? Hard to convince me that there is more air entering the chamber and that fallacy v. The Alpha.
Mikeinjersey
Well-Known Member
All well and good but if by chance you don't have baffles your bike may run well but it's not running its best for street use. Straight pipes are for dragstrip balls to the wall use not cruising between 2k and 4k like where most of our street riding takes place. If your issue gets worse start checking for intake and exhaust leaks. Also the carb adj Mr. Wright suggests can be very simple but very important for a proper running machine.
What Mike is saying is that there is no bottom end torque to keep the unspent from escaping. The reversion of that bubble in the reverse is to repack the unspent that leaves with the spent. Think of a bubble in and bubble out. Without baffle, the unspent bubble that came in is cut off by a 1/3, and 2/3rd is fired off = Lost torque.
With baffle, we add the exaggeration with a 1/5th of a bubble is cut. You feel this torque because there was a restriction to slow down the unspent from leaving along with the spent. You make more torque stopping the bubble from losing gas to make more gas heat up the air = Low torque.
If you can stand the torque you have now, up to you. Riding it this long you should have burned out a piston or two so it's not some out of rich jetting to cool it down. Still ain't broke.
With baffle, we add the exaggeration with a 1/5th of a bubble is cut. You feel this torque because there was a restriction to slow down the unspent from leaving along with the spent. You make more torque stopping the bubble from losing gas to make more gas heat up the air = Low torque.
If you can stand the torque you have now, up to you. Riding it this long you should have burned out a piston or two so it's not some out of rich jetting to cool it down. Still ain't broke.
I believe i will find some baffles. Thanks. If i can fine some these appeared to have been cut
john sachs
Well-Known Member
What I've found, back in the day, is if your exhaust system has too large an ID for the size of the engine, the cones, at times, will improve torque a tiny bit, and cure a possible stumble when leaving from a dead stop. WARNING: Don't use any spray on coating on the inside of the pipes.
John
John
Mikeinjersey
Well-Known Member
I swapped out my V&H baffles for Big City Thunder baffles and they worked well. I swapped them back to the V&H a couple of years later because I wanted to go back to a quieter ride. They have several offerings on the website you may find what your looking for. https://bigcitythunder.com/
Did you use the original hole in the pipe to hold baffle in or move it farther up?
Mikeinjersey
Well-Known Member
I drilled new holes the original was too close to the end. These are the recommendations/instructions that came with the Baffles. I mounted mine with the lollypop toward the end of the pipe as shown in the first illustration.
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Yeah i have the instructions, For some reason on the big radius the lollypop goes twords the engine
Mikeinjersey
Well-Known Member
I'm not sure why you say that but as long as your 3" from the end of each pipe you should be ok . The sheet says the sound and performance may differ a little but it's only what you prefer. Maybe they updated their instructions and I'm mistaken. You could also call them for clarification, can't hurt.