How to Rebuild a Vespa Clutch
I was working on getting this scooter ready to drive after a long hibernation, and found that the clutch was stuck. The plates must have gotten gelled together, which is not totally uncommon for scooters that were sitting for a long time. Time to pull the clutch and replace the clutch plates!
First, I got the scooter up on my lift. I put the centerstand on a two-by-four to get it lifted up a bit, then I clamped the front wheel in the vise on my lift. With the rear wheel up in the air, I could start working. I pulled the bottom rear shock bolt from the motor, and let the motor drop a bit. Then I removed the rear wheel.
With the rear wheel off, and the motor clear of the rear shock, I have access to the clutch cover. Pull all three bolts from the clutch cover.
With the bolts off, the clutch cover comes away from the motor. For ease of re-assembly, I leave the clutch cable attached to the clutch arm, and simply move the whole cover down, and away from the motor. Next, pull off the push pad at the center of the clutch. That gives you access to the clutch nut. First, removed the tab from the clutch washer that is pushed into a groove on the clutch nut. The clutch nut is a castleated nut, so you need to use the special clutch nut tool to remove it. I put the clutch tool on the end of a very long "wobble"socket extension so I can get my air-powered impact wrench to work on the nut. Make sure the clutch tool is totally centered on the nut. If it is not centered, you risk messing up the notches in the nut, and making it a lot harder to remove. With the nut off, you can use two screwdrivers on opposite sides of the clutch as levers to get it free from the crankshaft.
Here is what the inside (crank side) clutch looks like when it is removed from the motor.
I used the special clutch compressor tool to get the clutch apart. Here it is with the new clutch corks ready to go in.
While it is apart, I replaced the two brass bits on the drive plate. The brass bush at the top of the photo is particularly important. It can not have any play, and must be 100% snug on the drive plate. If either of these brass bits are damaged or loose, it will cause clutch grab.
With the clutch back together, line it up with the woodruff key on the crankshaft, and press it on the crank. Fit a new tabbed washer and clutch nut. Then tighten them down. Use a torque wrench set to 4-4.5 kg/m.
Refit the push plate. Then put the clutch cover back on, making sure that the brass push pin is located in the clutch cover. Tighten the three clutch cover nuts snugly. Then test that the clutch is correctly adjusted. You can do that with the motor off. Simply pull the clutch lever in, and start to move the kickstarter by hand. As you let the clutch lever out, you can feel where the clutch starts to engage as you move the kickstarter. Adjust the clutch cable as need be by using the adjuster on the motor. It is a lot easier to adjust it while the scooter is up in the air and the rear wheel is off! When you are satisfied that the clutch is adjusted correctly, then re-fit the rear wheel, and you're done!