Its hard to really describe. I don't even know if its really a problem, or if I'm just being picky. It just kinda feels like the shocks rebounding over bumps, but the fact that the bike is leaning at the time makes it feel like its wiggling a little. Not a lot, not like I'm on the verge of losing control, but enough to make me think twice about pushing it real hard. I know its not a sport bike, it just makes me wonder if I can improve it.

 

How many miles on those 04 stock shocks? Ohlins might be your answer. Give Howard at http://www.motorcyclemetal.com/ a call and explain this to him. He'll ask you a bunch of questions, and then tell you everything you ever will need to know about suspensions, and what shocks are best for your riding style.

 

Maybe I missed it in your post, but what pressure are you running in your shocks?

 

I had a similar problem but became progressively more severe real quick like. My issue turned out to be 3 broken rear spokes. You did not mention wheel type so if you have spokes check them out before it becomes a true death wobble. Try nearly losing control at 80 MPH. Some full blown pucker factor there....

 

I know exactly what you are talking about, your front and rear suspensions are working at different rates, or "out of synch", combined with the fact the suspension is pupming up and down while traveling, which causes a little wobulation through sweepers. When seeking to upgrade suspension, in addition to improving both the front and rear, they should be tuned to work together for the best results. Yes it can be greatly improved, I only know what I know, but ditching the progressive rate springs is a good start point, and the fliud change in the shocks is a good interim improvement, for the cost of a quart of fluid and your time, until you can get some better shocks.

 

You didn't mention how many miles on those stock shocks.
I replaced the stock shocks on my '02 Ultra last year because the dust boots were disintegrating. Picked up some "0" mileage takeoff stock shocks from an eBay seller.
They made quite a difference! I wish I'd have changed them sooner. They weren't leaking but maybe the seals and valving were bypassing.

 

I had a thought. I haven't played with the air in the rear shocks much. Manual says 0-10 psi, and I have it around 6. Wonder what difference it would make if I made some adjustments there.

 

The shocks have 18000 miles on them. I just bought this bike used last year, I assume they are original.

 

It may not be the miles, but the age. You could try letting all the air out and then fill them to about 10 pounds. But I'm thinking better shocks are in your future. How do they handle bumps? Are they soft or do they ride like a lumber wagon. If the ride is floating you may not have enough rebound.

 

How many miles on the tires - especially the rear? And are they the stock size?

I've found as the tires get miles the original profile changes since the rear tire wears mostly in the middle of the tread. A "squared off" rear wil handle poorly.

I guess my input is this - you won't know what you've got until you rule out the tires.