Ok, you may have just solved my clutch issue.
I have an 08 SEUC. The clutch started slipping a few weeks ago. I took it to the dealer and they said that the clutch plates were worn below minimum specs (very hard to believe when the bike only had 14K miles).
They replaced the clutch plates (wearable parts are not covered by warranty) and charged $300. Clutch plates did not fix the problem.
Then someone here mentioned that the clutch reservoir could be too full. I checked it and it was over-filled. Removed all the fluid - flushed out the reservoir and line - new fluid and bled the air. It seemed to be fine for a week... even took a 500+ mile trip with no problems.
This past weekend was on a 700+ mile trip and the clutch starts slipping again.
I have determined that it is heat related. When the bike is all cooled down and the outside temp is cool there are no problems. When the bike is at normal operating temp and the outside temp is 90+ degrees, the clutch starts slipping.
Took the bike back to the dealer yesterday morning and told them that the $300 they charged me did nothing for the clutch problem. the service writer said that he would call as soon as the tech diagnosed the problem. They have had it two days now, and no call yet.
When the bike is hot, the air temp is hot, and the clutch is slipping, it is like a cable actuated clutch that is out of adjustment.... the clutch does not engage until the clutch lever is almost completely released. When everything is cooled down, the clutch lever feels normal.
I kinda wondered if maybe the spring could be weak, but a failing master cylinder makes more sense... maybe?
LRebel, I have a couple questions for you.
Over the past 14k miles, before the new clutch plates, did you add fluid to the clutch master cylinder?
Let's assume that you have added a bit here and there.
Just like brake pads, when you put new ones in they push the caliper pistons back into the body. This pushes fluid back into the master cylinder.
If in your case you did add fluid over time, the overfilled master cylinder would be a result of the new clutch plates being thicker and pushing the clutch slave piston back into the bore and over filling the master cylinder.
Also when the clutch does slip, have you pulled on the clutch lever to see if you've lost your free play in the handle? If the handle free play has not changed then you have something inside the clutch giving you fits. If the free play is gone and the bike thinks you have the lever pulled ever so slightly, fluid expansion could be the issue.
One last observation from the old VW days as well as my '76 FLH rearbrake issues.
Let's just say that you have a car with the brake pedal not returning all the way to the out position, like in the old Beetle days when the brake pedal would rust and bind up a bit. If the pedal does NOT return to open the ports in the master cylinder, the pressure will continue to build up and the brakes will start to drag until they lock up. I had the same issue with the rear master on my old '76 FLH. I didn't pay that much attention to the brake pedal only that I had brakes. Until I finally rebuilt the rear master cylinder, the rear caliper would just start to bind up until it was smoking. I'd have to stop and play with the pedal to get the piston back out and then the caliper would release. My front master cylinder piston stuck in a bit too. It didn't feel bad because there is no direct hook up between the lever and the piston, only a push rod. There is still a small spring that returns the lever back out, but the pistion could stop 1/8" short and cover my return port in the cylinder.
This may not be your issue, but it only takes a minute to check it out.
Good luck with your issue with the clutch.