New plates should be cheap, soake for 24 hours min in motorcycle oil then install. New springs will likely make the most difference, they get soft, but make sure you have the clutch packed exactly right. My 450 had slippage and I bought new friction plates, when I was going to install I havd the parts fiche exploded view printed and as I unpacked the basket, noticed the PO have reversed 2 plates and it was the reason it was slipping at higher RPMS in the higer gears. It really is easy to do on some clutches. I almost did the same then noticed one plate looked a little different from the rest, looked at the fiche, that plate had a diff part number and it had to go in the right direction, after the plates, new springs the clutch looked up and the bike hauled ass. I couldn't get past 75 mph before, well over the ton after.