Ok guys, I need some help here!!! I have a 2008 Street Glide I bought from my brother in-law 14 mos ago with only 4500 miles on it. Since that time I have done many things to make this bike my own and have put 11,000 miles on it. In June I put on a set of S&S Power Tune Dual head pipes, and had it Dyno Tested. Since then I have been experiencing a vibration/knocking feel between 2700 and 2900 rpms and really bad under a load. There was no noise to be heard even when my local dealer put it on the Dyno to help me find the problem. After a thorough inspection of the mounts and the whole outside of the engine we could not find anything wrong. This past week I made a trip to Arkansas with some Buddies and found that if I turned the bike off and on twice the vibration would go away and I could fly down the Interstate vibration free. So when I got back and after some guys I talked to on the trip advised me it could be the old style compensator, I had it replaced with a new screaming eagle comp. When my local dealers service manager delivered it to me at my fire station he told me, "Problem Solved! runs smooth as new now" NOT!!!! When I got on it after work I immediately noticed it started better, the clutch felt different, maybe a little smoother and it definitely shifted better, but I still felt the vibration/knocking(but a little reduced). Now after a weekend of riding, the cranking is not as smooth, I feel a vibration through all the gears and especially under a load and I even noticed that when I pull the clutch in and coast, the bike vibrates moderately, and if I give it a little throttle it smooths out just a bit but is still there. THIS IS DRIVING ME CRAZY!!!! almost to the point of trading up to a new one. But mine is paid for and I am not fond of having payments again. Can anyone please help????

 

Your description of the vibration/knocking is kind of vague. Do you feel it in the seat, bars, foot controls?
Sometimes changing the exhaust can alter the harmonics of the whole system and this might be what you're feeling. Not sure how turning it on and off would make any vibration. I was thinking motor mounts but you say the dealer checked those.
Put a socket on the tank bolts. Even if it's a quarter turn loose that can make it shake.

 

Sorry about that, it is vague now that you mention it. I feel it in the highway pegs and the foot boards and at its worst it would feel as though the motor was fixing to blow. I just got done crawling all over it with it cranked and sitting still it sounds perfect. But when I get to certain rpm's and under a load the only way I can describe it is it feels like popcorn popping ball bearings as I ride down the road. I know that sounds stupid but that is the only way to describe it. The service manager felt it on the dyno but couldn't figure it out. It is now constant with the new comp and before it was intermittent. I don't know why but on my trip at 70mph it felt like it was going to blow the motor, but I got off the interstate and turned it off and on twice and it went away. This worked up until I turned it off again, so I just made a habit of filling up without turning the bike off.

 

AND.....I have contacted S&S technical support and picked their brains too.

 

If it can be stopped as you say by the turn off turn on cycle it is in the tune or a failing ECM would be my area of focus.

 

It could be stopped prior to replacing the comp, now it seems constant and I cannot get it to stop. Still feel it in any gear.

 

Would unplugging the ECM be worth a try? I know when I unplugged my Power Commander III the bike came alive and purred.

 

Excuse my ignorance but where is the ecm located, the local dealer used a tts master tuner for the dyno and the box they gave me when they were done had a module in it. I do plan on visiting them tomorrow with the tuner.

 

check your front engine mount

 

I have a 2007 SG and it's behind the right side panel. Take off your right side saddlebag and pop the plastic panel off that sits right in front of the saddlebag.