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Decel popping

Started by DYankee, June 23, 2020, 06:30:37 PM

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DYankee

My experience has been when a bike has decel popping it's always been an exhaust leak.

I just put in a 120ST and it has popped a lot from day one. I've got a Powervision and I tried to autotune after installing the motor, but it didn't help. I loosened up the exhaust and retightened it from the heads back and that didn't help.

Finally decided to get it dynoed and the tuner charged me an extra $350 because he said he had to put new exhaust gaskets on it.

Thing still pops too much. I've never dealt with the dyno guy before and don't know how good he is.

Could it be something in the tune that would cause the popping?
Double Dark 13 Ultra Limited
11 Wide Glide

Coyote

Quote from: DYankee on June 23, 2020, 06:30:37 PM

Could it be something in the tune that would cause the popping?

:koolaid3:

Ohio HD

I'm far from a pro tuner, but what usually works for me is add timing to closed throttle decel. If that doesn't work, add a little fuel as well at decel.

Pirsch Fire Wagon

1. Check the intake for Leaks with Propane - "most times" a good tune will be altered by an intake leak allowing inaccurate AFR Ratio at the Cylinder and not the Throttle Body/Intake

2. If that checks out,

a. What type Fuel? Ethanol, non-ethanol? Octane?

b. Using AFR or LAMBDA?

3. This sounds counter-intuitive note where, speed/RPM the popping occurs and add fuel in that cell and the surrounding cells x 3. Min AFR 13.9 (L 0.94) AFR 13.2 (L 0.89).

4. I find it all but eliminates it 100%
Tom

DYankee

Thanks Ohio I can do that with the quick tune.

Fire Wagon- Fuel is sometime 10% corn, 91 to 93 octain
Don't know about lambda or AFR

Propane just sounds scary, but I will see what I can find on an intake leak.

Thanks for the help.
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HV

Carb cleaner or Contact cleaner will also work and is much safer..... Using Quick Tune ...in fuel Tab on Decel add 5 % ......in Spark Tab in Decel add 3 Degrees   try this   adding more fuel and timing can help if still an issue... but if you need to add too much you have another issue
HV HTT Admin ..Ride Safe ...But Ride informed with HTT !!
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aharp

All of the above, but also sometimes the exhaust design is what causes it no matter what you try with the tune. You don't say what pipe you're running (unless I missed it somewhere) but sometimes the best you can hope for is to get it down to a blub blub sound instead of a pop pop.
Speed costs money. How fast do you want to spend?

Hilly13

Your decel VE's could be be way out, if you follow me, do some tuning runs on a steep downhill with varying throttle open positions in as many gears as you can, I have seen ve tables from a very competent dyno tuner that beggar belief, push them down, retest and back up they come, they want what they want, start there, chucking fuel and spark at it might work, but if the timing tables and afr tables were developed on a similar build I'd be looking at ve first.
Just because its said don't make it so

Coverdog

Quote from: Ohio HD on June 23, 2020, 07:05:01 PM
I'm far from a pro tuner, but what usually works for me is add timing to closed throttle decel. If that doesn't work, add a little fuel as well at decel.
Old thread, but I have been trying to eliminate decel popping On a 96" with Rinehart 2-1 pipes. I was able to get rid of most of it but occasional single pops and spitting on decel. I always read to increase fuel and timing and was at 15% fuel and 5 degrees timing and didn't want to go higher due to increased fuel usage. I figured that was the best I was going to get with that exhaust.

After reading your post I went back to zero decel fuel and kept the 5 degree timing advance. No more pop, thanks for the tip.

Ohio HD

Quote from: Coverdog on July 22, 2020, 05:03:27 PM
Quote from: Ohio HD on June 23, 2020, 07:05:01 PM
I'm far from a pro tuner, but what usually works for me is add timing to closed throttle decel. If that doesn't work, add a little fuel as well at decel.
Old thread, but I have been trying to eliminate decel popping On a 96" with Rinehart 2-1 pipes. I was able to get rid of most of it but occasional single pops and spitting on decel. I always read to increase fuel and timing and was at 15% fuel and 5 degrees timing and didn't want to go higher due to increased fuel usage. I figured that was the best I was going to get with that exhaust.

After reading your post I went back to zero decel fuel and kept the 5 degree timing advance. No more pop, thanks for the tip.

Different exhaust and motor configurations all react a little different as far as what works and what doesn't to eliminate popping through the exhaust. Sometimes you just need to try a few different methods. I'm not the tuning expert, but I've always started with timing first, then ease the fuel on if needed. Glad you got yours sorted out.