I just got my Ultra a couple of months ago, and I ride to work most days. The last 1/2 mile of the ride is all down hill and lots of times I just coast, let go of the bars and relax. At least that's what I did on my last 2 bikes.
When I do it on the Harley the front end shakes and I have to grab the bars to keep it from shaking. I've also noticed a slight wobble when slow speed cornering.
Can anyone tell me what causes it, and how to fix it?

 

Wheel out of balance, low air, tire has cupping, might be worn to the limit, fork oil might need to be changed. Looseness in the forks or neck bearings, might need grease. Springs might be getting weak, maybe just one spring. I would look for the most obvious things that are easy to check before tearing it apart.,,

 

Harley's touring bikes are well known for this.Check out a true track stabilizer at www.truetrack.com.

 

big cahuna has you covered here, I may just add to check out the fork oil levels in both sides to be sure they are even and filled correctly.

 

You didn't say what year Ultra, but there was a problem with the front tire on the '09s. Harley had a recall and replaced the Dunlop 407s. Might check on that.

 

It does not sound like the "bagger wobble" I have had. I upgraded with the Glide-Pro system. Very happy with the result. www.glide-pro.com

Moe