Slipping clutch
HAL,
Get yourself some 60 grit Wet-or Dry paper on a sanding block and start laying into the glazed sections until they look like rough new friction material. Reassemble it, warm the engine up, and take-off holding the throttle wide open. It'll slip for a while, maybe a long while, but as it heats up it will start to hook up. Do this a few times and if it doesn't engage satisfactorily, disassemble and repeat the entire procedure, as many times as necessary, until you have contact over the full length of the friction material. When you see full length friction material contact you will be pleased with the clutch function.