Serafin,
There won't be any "service bullitins" on the KX500, or any KX for that matter as it is intended to be a "competition" based model. There might be however "service updates". In my experiences with Kawasaki, when a brand new chassis is released, there is a TON of updates the second year (the KX250F is a perfect example, it5 had a lot of changes the second year of production). The chances are slim, as the KX5 has not recieved any significant engine/chassis upgrades since '89. I will do a dealer service inquirery to see what I can dig up.
Rich