I have the same sound, when in high gear, low RPM and do a full throttle...annoying..

 

Has anyone tried to tune it out? Anyone running a stock motor(harder to find than the bigfoot) not even stage 1 have the issue.

 

I have a Stage 3 EVO and was getting this under hard acceleration since I installed hi-comp pistons. Always ran 93 octane and booster and still got noise. Finally had the bike dyno-tuned and adjusted ignition timing. That got rid of about 90% of it and performance didn't suffer.

Also had the heat shields doing the same thing years back but that noise was on the right side and usually at idle. Drove me nuts though until I started checking nuts, bolts and screws for tightness.

 

It doesn't look like anyone posted what I found so here we go. I had the same type of sound under the same circumstances so I started it in the garage, and searched for the tinny rattle sound and found it. On the rear fender there is a thin piece of metal on the inside of the fender on each side that connects to the front and rear bolt of the fender struts. I would rev it then hold one side and it went away. The middle of the bracket vibrates against the fender. Nothing a little double back tape will cure.

 

Didnt read the whole thread so may have been talked about

It can be caused by running lean at the higher throttle postions

Mine did this when I had just the slip-ons on the bike. Now that I have added the SE breather and a PCV it no longer does it.

 

Control group here. I'm running a Bone-Stock motor (it's an 08 SB) with Syn 3 all the way. Have about 6k miles on it, and have experienced the noise under wide open throttle from mid rpm range and up. As stated before, it sounds like tiny rocks flying AT the motor from front tire. On yesterday's ride I was listening for it and found it accellerating hard up a steep on-ramp. Decided then that the sound was definitely coming from the front of the exhaust (not the back), and I'm fairly certain that it's the exhaust "settling." I think it's either a heat thing, a pressure thing, a vibration thing, or any combo of the three, but I'm fairly certain that it's coming from where the pipe meets the front cylinder. Maybe a cheap-o exhaust gasket? I don't know, but I'm confident enough in it to not care. But it sounds exactly like if you were to fire little 1/8" rocks down the pipe from a BB gun. In the most extreme cases it's sounded a bit like the sound guy-wires slapping together make in the movies.

 

sounds like detonation..i would try a octane booster first (very cheap) also check the ignition timing, voes, and air fuel mixture. Harley set the bikes up really lean and in the summer the lean mixture plus the added heat can make the combustion temps and pressures increase dramatiacally. the 93 octane might not be enough with the other varriables...

 

Guess what? I noticed the same ting a couple of weeks ago. I been going crazy trying to figure it out. I am stock with stage one.

Shawn

 

I had the same problem and was 99% sure it was not any form of detonation. But I figured it was cheap enough to try filling my tank with premium for a test. I did (93 octane) and at least the symptoms of the problem went away 100%. Your mileage may vary but what's the harm in trying the high-octane stuff? None.
EDIT: To be clear, after my experiment I continued to run 93 octane and have put at least 4000 miles on the bike with the 93 octane gas in the bike and the problem has not resurfaced. I understand that the compression ratio of a stock Harley engine is low enough that it should not require the higher octane gas. I'm only reporting what I've personally experienced.

 

It could be any of the things mentioned but mine does it too, and at least it my case, it is detonation. If it is detonation in your case as well then try to avoid making it happen. Don't load the engine as much, use higher rpm and pay attention to where you get the gas that makes this happen. And of course, expect it to be worse in hotter conditions. Either way, detonation will burn a piston eventually so beware! All I can get in AZ is 91 octane so I may see it more than some folks.