A few days ago I posted a thread about a noise, rattling sound, inside the belt cover on my 2000 SP 500. A couple of guys responded and thought it was the drive belt(appreciate the help.) I also thought the belt was at fault, even though it has just over 500 miles on it. I checked with the local dealer who also thought it was the belt. However, after installing the new belt I still had the same problem. In neutral at about 2500 RPM the PVT pulley would shimmy causing the rattling sound. I loaded the SP and took it to the dealer. It took them a little while but diagnosed the problem in the drive pulley. After removing the belt and running the motor in neutral the PVT ran true. They put on a new drive pulley and presto, it was fixed. The belt was not riding in the drive pulley at the same depth all the way around, this caused the PVT pulley to vibrate at certain RPM. The drive pulley bushing was shelled out.
Hope this info will help someone out.

Was that a factory defect? Or, was it caused by something else? I'd be interested to know which.

The mechanic thought defective bushing. He said it may have been made by someone for Polaris and didn't meet specs, which may have caused the problem. He said it had nothing to do with improper operation. This dealer said he thought he could get it covered by warranty even though it has expired by one month. He was really helpful. The dealer I purchased from saved me about $500 the day I bought the SP500 but was very little help with my problem. He didn't even mention getting help from Polaris.
Guess where I'll buy next time!!!