Thank you all for the responses...I have a lot of car engine building experience and background...built, tuned, and raced high performance engines in stock cars and hot rods, and did a lot of rebuilding and tuning on carbureted dirt bikes, but new to the V twins and fuel injection. I haven't had a chance to investigate common lean condition issues or the tuning...but I will check all that out soon. Assuming it is not a lean condition or other tuning issue, I was kinda wondering if it might be a common issue that affected a lot of the V twins, or maybe specific types of muffler/exhaust systems?

I am just starting to read up on tuning for the efi...at this stage, I am not looking to maximize power or anything, just a good tune up. I prefer to learn and do tuneups myself...Appreciate any advice on how best to approach that?

I will try and post better closeups of mufflers for ID purposes, but can't do so until I return from a job assignment in a couple of weeks.

 

Funny how personal preferences go. I am led to believe the new Jaguar sports car has a device to inject fuel into the to exhaust to get crackle upon decal. Harley people tend to want to get rid of it.


All the hot truck people want auto trans and all the hot sports car people want manual boxes.


Makes the world interesting I guess.

 

What you are describing is known as decal popping. Those mufflers don't look like stock mufflers, so it is possible that they have been sucking cold air into the pipes ever since they were installed.
Since you don't know where to start I would suggest that you do like several above have suggested and that is to replace the muffler clamps on each muffler with new ones (about $10.00 ea.) Pay attention to where you put them on the muffler and absolutely, positively rent, borrow or steal a torque wrench to clamp them down with (around 42 ft. lbs. should do it.) You have to rule out any leakage of cold air into the exhaust pipes. If, after replacing the clamps it still pops, them move on to tuning. You would be surprised if you knew how many home mechanics think putting on their muffler clamps using the "armstrong" method was sufficient. Those muffler clamps are prone to stretching so I don't recommend reusing them unless you are destitute.

 

Exactly.

 

I am at my two local race tracks quite often, maybe 3 times a week some weeks.
If decel popping indicated lean running then virtually every race car and bike I see there is out of tune.
There has been SO much bad press about the decel pop that aftermarket tuners now have the facility to either turn off the spark or the fuel or decel.
Decel pop can indicate a lean AFR, but most of the time it doesn't, and is normal.

The worst thing you can do to get rid of it is cut the fuel on the over run, as unburnt fuel has a cooling effect.

All 3 of the Harleys I've owned have popped a bit on decel, and I like it, in fact two of them did it on standard pipes if you listened hard enough.

 

Decel popping may be common on Harleys, but it's not correct. Raw gas is igniting in the mufflers. Most common cause is an exhaust leak, and properly torqued new gaskets at the heads can cure that. You can also fix it by either adding more fuel (too rich to burn) or less fuel (too lean to burn) with zero throttle and low MAP. I don't know how much flexibility the older fuel injection systems have, but the PV on mine has an adjustment for tuning this condition out. My bike doesn't pop on decel, just a nice grumble when I shift.


ps race cars do it because the headers are so short air can get in between exhaust pulses and ignite the next one.

 

Thanks again for all the feed back everyone! I will investigate and fix any air leaks etc. And will tune AFR at some point just to be on safe side so as to not run lean and hurt valves.

The discussions thus far now leads me to two more questions about this...

1) Assuming all leaks are fixed and tuning is correct, is it possible or heard of that the muffler design itself can contribute to the popping?
2) If popping still occurs after fixing any leaks and proper tuning, is there any possible negative consequences to the popping? I am not really bothered by the sound or anything, I just want to make sure that there is no damage that can occur!

Chuck