How does your clutch look? It's the only other thing, could possibly locked and not engaging? Your machine still looks extremely clean so I wouldn't think it'd be clutch dust or premature wear, the disks for your slipper showing obvious signs of wear but I'm not sure what's considered excessive on that area
Either the clutch, bell shaft, or slipper has to be the problem. I put red loctite between my slippers when I reassembled mine...I didnt want mine to slip, I'm sure some cooked off from the heat, but seem to be getting power delivered evenly.