I did a forum search and GearNut had this to say about increasing clutch pad tension:
The main clutch spring that squeezes the clutch together is inside the transmission case, between the clutch and final drive sprocket. It is adjustable from the outside of the cases.
1. Remove clutch cable from engine.
2. Remove sprocket cover with clutch release lever.
3. Remove clutch cable stop from top of transmission. It just unscrews after loosening the lock nut that binds against the top of the transmission housing.
4. Find a strong flat bladed screwdriver that fits snugly down into the hole that the clutch cable stop was threaded into.
5. The spring adjusting nut is basically a threaded collar with 4 notches, equally spaced, cut around it's circumference. The trick here is to rotate the final drive sprocket with channel lock pliers or similar tool that will not damage the sprocket teeth.
Rotate the sprocket while pressing down on the screwdriver until you feel the screwdriver slip down into one of the 4 notches of the spring adjusting collar.
Once the screwdriver fits into one of the notches, the sprocket and sprocket shaft should be difficult to turn.
6. Hold the adjusting nut inside the cases stationary with the screwdriver and turn the sprocket clockwise to tighten the main clutch spring.
Do not adjust is too tight as doing so will only make squeezing the clutch lever harder, strain the clutch cable, and accelerate wear on the clutch release components inside the cases.
1/2 to 1 full turn should be plenty, but you may have to experiment a little (read do all of this over a few times).
7. re-asemble everything back together, adjust your clutch cable and flower nut back to "normal", and enjoy a clutch that actually puts proper pressure onto the clutch pads.
