Description
Some KML viewers will incorrectly display features if they have more than 30,000 vertices. If the original data had more than 30,000 vertices in a single feature, you may experience rendering issues in the KML client.
Solution
If the KML client is experiencing issues with rendering a particular feature, you can use a different KML client, such as ArcGIS Explorer.
Alternatively, you can modify the original data before converting it to KML. The Split tool or Generalize tool can be used to simplify your data.