I just replaced the front mount on my 2008 FXDL, only 16,400 miles. I have been having some unexplained vibration and I could not find it. I pulled the mount and found what I thought to be some hair line cracks along both front edges where the rubber met the steel and I see that the engine had been rubbing on the top of the portion that bolts to the frame.
After fitting the mount and putting in the 2 motor bolts, found that the new one was short from touching the frame. I raised the motor until the frame bolts could be turned in by fingers and figure this was a way to determine that things lined up properly. There was a 5/16" space between the mount and the frame.
Not sure what to do, and figuring that putting in the original bolts and tightening it down, would put LOTS of strain on a new mount so I put in the 5/16' of shims. Took it for a ride and I don't know if I have ever been able to see through my mirrors as good as I am now. Little to NO vibs in the pegs or hand grips. A little shake at lower speeds, stop and go traffic, but 65, 75 and +, smooth as silk.
Any thoughts on if I should have used thee shims? I know others have had similar issues and am wondering what they did.

 

I know of several members, myself included, who have shimmed the front mount the same way with the same results.

 

im going to do this same thing soon enough, replace the nount entirely and get it right myself.

 

I shimmed mine last week with a shim cut from a 1/8" piece of flat bar steel. Definitely reduced vibrations at all RPMs, but most noticeable from 2500-3500. At 3200 on the highway the mirrors are vibe free. Possibly a little more vibration in the front pegs than previously, but I haven't noticed much there to begin with.

 

That's just what I did, needed 1/8" and it really smoothed it out.