Exhaust popping

[Alan Shackleton]

Here’s one for the experts. 2003 Chopper, 4100 miles, 107 S&S, xXx carburetor, Super Trapp Mad Mother exhaust. All set up at factory when new. Exhaust recently removed and installed with new gaskets when broken cover shrouds were replaced. The bike gets periodic weekend use in Arizona spring and fall. It is very cold-blooded and requires the enrichener to be on for about 15-20 minutes. Then the engine will idle with it off. With the enrichener off, the engine pops when I roll off the throttle, changing gears or just slowing down. This isn’t new behavior, but I’m getting concerned it might be running too lean and I don’t want to burn valves. Not to be an a-hole....I’m not looking for guesses here, but if you’ve had a similar situation and found a fix, I’d like to hear about it. Thanks.


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[Billy the kid]

Look at your spark plugs, if they are a white color it is running lean.

 

[Fat_Bastard]

This happened to me when someone screwed around with my carb settings:
Had to go to S&S website, get the manual and reset 'idle mix screw' and 'idle speed screw' per specs, moving 1/4 and 1/8 turn to finally get it, then it went away... [Also be sure you have clean 93 octane or higher gasoline (no Costco, ARCO gas, or mid-grade mix, etc)]

Also in AZ right now and have to ask where you are? since places like Prescott, Flagstaff, etc... are very high altitude and can throw the settings off quick from sea level cities... (Chicago, Phoenix lower altitiude).

PS: Found the file from mine: see page 9, carb tuning guide.

 

[francoblay1]

Enrichener should never be on for more than 30-60 seconds!!!! Your Carb settings need a serious look.

What altitud are you at?
What jets are you running?
Is the mixture screw in good shape? (yes, they do get fucked up and need to be replaced, see pic... a groove/dent was formed from screwing that thing too far in by the previous owner... once I installed a new one all the problems tuning the Carb disappeared!)

Some files attached for you.

 

[HMAN]

Just saying.....do what other suggested. Check carb settings. But, S&S says that a properly tuned carb will exhibit decel pop. I kinda like it myself but Im a tad different. You will get it figured out...

 

[Alan Shackleton]

Thanks for the tips and the PDF files. I’m back in the Chicago area now and will make the adjustments on my next trip out. The Dog is mostly ridden in the north Scottsdale/ Cave Creek/ Carefree area and the altitude there is ~1500 MSL. All the current settings are from the factory setup and the bike was originally delivered to Chicago ~800 MSL. The settings have never been changed. Fuel is name brand (usually Chevron) high octane (no ethanol if it’s available) and it doesn’t matter if summer or winter blend, it pops regardless. My HD springer here in the Midwest only requires the enrichener for a minute or so when it’s cold, all the other bikes in the stables are EFI. One other thing, the idle mixture screw appears to have some sort of loose plastic cap on it. Does that just get pried off?


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[Alan Shackleton]

Many thanks to those who sent tips and documents. I’m back out in Arizona for Bike Week, so I got my handy screwdriver out and made the adjustment per the S&S carb tuning guide. It took all of a minute. It runs so much better. Then I was told that the carb had been adjusted so the bike could pass an emissions test years ago. Fortunately, it will never see another emissions test, so it is good to go. Still have some exhaust pop when it’s cold, but not like it was. Thanks again everybody. BTW, saw a dozen or so Big Dogs at Cave Creek Bike Week. We noticed there’s fewer custom baggers and more choppers this year. I like the trend.


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[SimpleMan_Omen]

If anyone else has a similar issue S&S has a YouTube video that shows you how to adjust the carbs and lets you hear what it sounds like with various states of mis-tuning to help figure out which part is out of tune.

 

[SEAL-rider]

Many thanks to those who sent tips and documents. I’m back out in Arizona for Bike Week, so I got my handy screwdriver out and made the adjustment per the S&S carb tuning guide. It took all of a minute. It runs so much better. Then I was told that the carb had been adjusted so the bike could pass an emissions test years ago. Fortunately, it will never see another emissions test, so it is good to go. Still have some exhaust pop when it’s cold, but not like it was. Thanks again everybody. BTW, saw a dozen or so Big Dogs at Cave Creek Bike Week. We noticed there’s fewer custom baggers and more choppers this year. I like the trend.


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You should tune for power, circuit transition, throttle response and maybe mpg.
If you tune for decel pop you will likely end up rich. No decel pop on mine is an indication of rich condition.


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[Alan Shackleton]

You should tune for power, circuit transition, throttle response and maybe mpg.
If you tune for decel pop you will likely end up rich. No decel pop on mine is an indication of rich condition.


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It runs and sounds better in every regard after tuning per the S&S guide. The throttle response is way better. Before the adjustment I had to use the enrichener to keep it running and would get about 85 miles before needing to switch to reserve. Now I get 115 miles before switching. So the bike runs better, sounds better and gets about 30% better MPG. That’s a win if you ask me.


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