Here's a mod to minimize vibration in the handlebars of the bike.
This is Shawn's mod to his '86 Kawasaki Concours:
I just received my 2000 handlebars to add to my '86 Concours and was surprised on how light they were. My FJ1200 handlebars weigh in it like 6lbs for the set compared to what feels like 1 lb for the extruded aluminum handlebars of the Concours.
People have mentioned filling them with with lead so I started looking around the garage at my boxes of left over bike parts and bolts. I found a axle bolt the would fit inside the handlebars once you made sure the weld was smooth going into the handlebars. If you look at is you will see the weld puts a small shoulder that reduces the inside diameter of the hole. I only had one so measured it and it turns out it is a 5/8 hole. So down to the local ACE to pick up a couple of 5/8 bolts. the longest they had was a 6" bolt.
So took it home whacked the head off of it and stuck it in the inside of the handle bars. It really is not totally long enough as you need a 8 1/2 long bolt to go all the way to the end of the bar. However the damping effect of more mass at the end of the bar plus more overall mass is what i am looking for. I put some premium silicone window caulk in first to seal the one end and then more window caulk on the dash side to hold it on that side and prevent vibration. You could do this all on the bike and remove nothing which is the beauty of it. All you have to do is remove the black plastic filler plug to get access to the inside of the handlebars.
Put it all together and drove it. Now I also swapped to 2000 handle bars from 86 at the same time so I can not claim all the damping is going to come from filling the handlebars. I took it for a short drive last night and it did seem to help a little bit on the 4k to 5k buzz that I have on this bike.
Oh yeah cost - $7.50 for two bolts, $4.50 for premium silicone window caulk.
Here's a picture of cutting the bolt heads off, one is already done.