Dry clutch, L&T Mini, Patriot, Horstman and Tomar are all good clutches. Comet and Woltjer build good KT100’s. For peak performance 4hrs on a top end. Club racing you can go 8 hrs on a top end but that’s pushing it a bit. For every 2 top ends do the bottom end. Clutch stall speed 8600-9000 depending on a can or pipe but you can get that info from your engine builder. Always keep the clutch drum lubricated with Tri Flow. Also it’s best to change the carb pumper after every couple of race days.