be experiencing what is known as "flutter". But first a question: Does this wobble happen while your hands are on the bars or off? Flutter is when the bars wobbling back and forth when no hands are on the handle bars (no dampening). Flutter is considered by many to be normal at speeds above 15-20 mph; however it can be minimized or almost eliminated with proper weighting (balancing) of the tires. I have found the use of Dyna beads to virtually eliminate the "flutter". Dyna beads are tiny beads that are kinda like BB's that go inside the tires or tubes. They replace traditional wheel weights. I can't explain the physics of how they work, go to their website and watch the video. To me it's pure "PFM".
I don't sell them and am not affiliated with any shop so don't think I'm trying to sell something. I use them in the tires on my Electra glide and I cannot tell you how much it changed the ride. The whole front end smoothed out and vibration was dampened (you can't eliminate it all).
Dyna beads are cheap and easy to install. I paid about $15.00 for both tires. You simply insert them through the valve stem, re-inflate the tires and done. Takes less than 15 minutes.
Dyna Beads for Motorcycle Riders and Dealers
I don't know if this will fix your issue, but it's cheap and can't hurt to try it out first.
Just my .02 worth.