It seems that many of you are having problems with the generator pulley exploding. In most cases, the cause of this is not having the correct number of shims. You must have a total of at least 8 shims. If you don't have the correct number of shims, the bell will not tighten on the outer half of the pulley, which will allow the pulley to stay loose. In other words, the inner diameter of the bell bottoms out on the shoulder of the rear half of the pulley. This leaves the two pulley halves loose. They will work against each other causing them to explode, not to mention, it ruins the key way slot on the generator shaft itself.
Many people tell me "mine is fine and I only used 4 shims". Not true - the belt is holding the halves apart, giving the illusion that it's tight. So make sure you use 8 shims. What you don't use between the halves, use under the bell. If you've already thrown a pulley, putting 8 shims on now may not cure your problem. In most cases you have wallowed out the key way slot on the generator shaft, if this has happened to you, the only way to fix it is to replace the generator or disassemble the generator and take it to a machine shop and have a new key way cut into the generator.