Thought you may want to read this post from another forum about clutch problems with some Sporty models that sounds similar to what the OP is experiencing.
Clutch Alert!
Just a head's up on a real problem with the Sporty clutch. The stock design uses an additional spring plate in the center of the clutch pack. It is a double plate with small springs between the main plate. These plates are all held together by brass rivets.
Those rivets are the weakest link in the entire drive mechanism! My first clutch went out around 25,000 miles. At first I just thought I could adjust it. Could never get it adjusted right. Finally took it to the dealer (it was still under warranty) and they thought they could adjust it. After working with it for about 4 hours, the dealer decided something inside was screwed up. And they ordered everything inside that could possibly be wrong so they could make a quick repair for me.
Two weeks later, the parts were all in, and I was able to make the trip to that particular dealer. Once they opened up the clutch basket, it was a surprise to all. Everyone of those rivets and springs had come out, and had been floating around inside. That had caused the clutch hub and Shell to also be trashed. They had not ordered a shell or hub, and I couldn't fault them for that.
When my last clutch started failing, it was showing the same signs (after 40,000 miles on the second clutch). The signs of the center spring plate coming apart is that the clutch will both slip and drag. In theory that's impossible, but that's how the clutch reacts to those extra parts floating around inside the clutch basket.
The only clutch I could find that doesn't use that same center spring plate design was the HD Screamin Eagle clutch. It replaces that center spring plate with 2 extra friction plates and steel plates. Word of caution if you deside to go this route....that is one freekin stiff clutch! Part of the reason for the center spring plate design was to make the clutch pull easier, and then the outter spring also has to be stiffer on the Screamin Eagle clutch. Between those two, it makes for a very hard clutch pull, also a very reactive clutch. The friction zone is small on the SE clutch. Once you start letting it out, that baby will GO.