Popping on decell

[Twistedspoke100]

So I know popping on decell is almost unavoidable sometimes but it seems like its happening way more often then it did before it was put away for the winter. I am running a S&S with a Thunder jet and RnB 2 into 1 pipes with a baffle if that helps. The question is there something I should look at first or is there a tuning trick I should look into to help make it less.

 

[Pddain]

S&S has recommendations in their manual on the carb. Below is what I had and how we fixed it. I do have baffles and added thunder head baffles, plus what we did to the carb as described below.

Ok, probably the last installment. Recapping, I had a rough running engine between 2000 and 3000 RPMS with severe decel popping any time I let off the throttle even slightly. the bike felt like it was running out of gas when trying to cruise below 30 (2300 to 2800 RPM). The throttle was very sensitive and difficult to control

I followed the S&S recommendation on jetting and put a 60 in the main jet air bleed. My mechanic put a screen on the intermediate jet to atomize the fuel. We then added lollipops to increase back pressure and increase exhaust gas speed. We did not remove the intermediate bowl vent plug, as recommended however.

Results
The throttle is very responsive but smooth through the entire range. Cruise in the 2000 to 3000 RPM range is smooth and comfortable, jerking is gone. Decel popping is dramatically reduced, vibration has reduced significantly. With V&H 2 inch, 2 into 2 short pipes and a cone air cleaner, the decel popping won’t go away, based on my research, but the bike runs great, and the barking is minimal. There is a felt increase in torque but a Dyno is not in my current budget.

thank you all for the guidance. You are all the best.

 

[bdm7250]

So I know popping on decell is almost unavoidable sometimes but it seems like its happening way more often then it did before it was put away for the winter. I am running a S&S with a Thunder jet and RnB 2 into 1 pipes with a baffle if that helps. The question is there something I should look at first or is there a tuning trick I should look into to help make it less.

I have mentioned this many times before on here:

Decel pop is normal for a bike with open exhaust and open A/C that has a performance tune.
Decel popping does Not damage your engine...it is simply unburnt fuel that is burning in the exhaust tract after exiting the engine.
But a lot of folks don't like the decel pop and try and tune it out.
Decel popping occurs when one of two things are present.
1. The bike is so lean the exhaust is superheated and is burning the unburnt fuel that is in the pipes (there is always some unburnt fuel in the pipes no matter how lean). This is very rare, and does not sound like it is what you are experiencing.
2. The AFR IN THE pipes is just right to burn the unburnt fuel. This is quite a common occurrence when free flowing pipes are installed (whether or not a free flow A/C is installed). It can also occur if there is an exhaust leak that is introducing extra air into the exhaust tract.
Check for leaks...if there are none, then move on.
To get rid of decel popping a lot of people put MORE fuel than is needed into the engine/over-richening the AFR so that more unburnt fuel goes into exhaust, changing the AFR in the exhaust so that is no longer optimum for combustion in the pipes. This is just a waste of gas.

 

[Pddain]

I am living with a little popping as the way the engine is running is spectacular. It took the effort above to get it there however. The diffuser on the intermediate really helped.

 

[Mikeinjersey]

So I know popping on decell is almost unavoidable sometimes but it seems like its happening way more often then it did before it was put away for the winter. I am running a S&S with a Thunder jet and RnB 2 into 1 pipes with a baffle if that helps. The question is there something I should look at first or is there a tuning trick I should look into to help make it less.

I think the way to look at this is that the popping is worse today than it was before the Winter nap. I would check for possible new vacuum leaks around the intake manifold first or maybe a cracked rubber cap on the vent. If no leaks drop your bowl a clean it along with the jets. As bdm7250 explained it's an air/fuel issue and since you didn't do anything to change that (like new pipes or removing baffles) a new vac leak or slightly clogged jets would be worth looking into. Both are virtually free to check and also it's always nice to have clean carburetor. Good Luck
This is the S&S adj guide if you have no success and need to tweak. Do this last not first.

 

[Jersey Big Mike]

I concur with the clean jets and bowl perspective as with current fuel clogging can be a real issue.

But on the overall issue, as someone once told me

"It's a dog, let it bark!"

 

[Mickmorris]

S&S has recommendations in their manual on the carb. Below is what I had and how we fixed it. I do have baffles and added thunder head baffles, plus what we did to the carb as described below.

Ok, probably the last installment. Recapping, I had a rough running engine between 2000 and 3000 RPMS with severe decel popping any time I let off the throttle even slightly. the bike felt like it was running out of gas when trying to cruise below 30 (2300 to 2800 RPM). The throttle was very sensitive and difficult to control

I followed the S&S recommendation on jetting and put a 60 in the main jet air bleed. My mechanic put a screen on the intermediate jet to atomize the fuel. We then added lollipops to increase back pressure and increase exhaust gas speed. We did not remove the intermediate bowl vent plug, as recommended however.

Results
The throttle is very responsive but smooth through the entire range. Cruise in the 2000 to 3000 RPM range is smooth and comfortable, jerking is gone. Decel popping is dramatically reduced, vibration has reduced significantly. With V&H 2 inch, 2 into 2 short pipes and a cone air cleaner, the decel popping won’t go away, based on my research, but the bike runs great, and the barking is minimal. There is a felt increase in torque but a Dyno is not in my current budget.

thank you all for the guidance. You are all the best.

So glad to hear you got your bike running exactly like you are wanting. Hopefully no more low air pressure in the tires! Lol

 

[Pddain]

Lol. That tire is still holding. Go figure.