Mike, you might start with the spring-loaded belt tensioning idler under the seat:
[Linked Image]

It sometimes doesn't quite click into the next position, and you have to push it forward with a small bar (or sometimes with the sole of your boot) until you hear the click. The design is a bit marginal - it should always take up the wear automatically, but it is not at all unusual for it to need a bit of help. If this isn't clear just say so, and I'll go into nauseating detail.