That's how it was described to me by an indy tuner who works on Harleys and some other high [performance V-twins. I have a 2004 Heritage, efi, 95" kit with SE flat top pistons, andrews 26 cams, samson true dual head pipes and rush 1.75" mufflers. It has a PCIII and has been dyno tuned (76 hp, 92 TQ). When I let off the throttle I hear a "tweeting" sound from the exhaust. It's not popping or backfiring. Pretty much happens until I pull the clutch. The indy tuner looked at the dyno sheet, took it for a test ride and said he thought it might be a muffler or baffle design issue. Said he could take my money and put it on the dyno but didn't think it was a tune issue. Said the bike ran great. I pulled the baffles and found the baffle wrap was all mushed down in one end. I repacked with 5/8" stove rope. It sound a little better but still makes the noise. Anyone know what this might be?

 

I just can't resist. Did you check for a bird nest in the exhaust pipe? Sorry.

 

If the baffles are not too hard to take out get to the stove pipe material or add some loose unravled material around the area where its close to the outlet.

This stuff, when you run, will work its way to the least resistance and maybe plug the tiny leaker.

Doesn't hurt performance. If anything the sound will be deeper. Better than Tweeting.
Been there.

 

Old Gunny. Thanks for the reply. I'm a little unclear on what you are suggesting. Should I pull the baffles and pack some loose fiberglass insulation around the stove rope? When I wound the stove rope on the baffles I did it loose but each coil of rope was touching the next and it covered the baffle openings completely all the way to the wider flanges at each end of the baffles. I figured by doing this it would not slide down the baffles.