Here's a perfect example of what some of us SP1 owners have experienced if our clutch system isn't in top notch maintenance.
Even after completely going thru my system, every thing from new internals in all cylinders, fluid flush, new clutch plates and springs, pazzo handle - I still get the occasional judder from my clutch. Usually only when I've been riding hard on older engine oil.
I've done enough research, I'm convinced that a SP2 clutchplates/discs will fit the SP1. SP2 includes judderspring
Watch right at about :37