Hi I just got a 2005 Polaris predator 500, I was looking around inspecting it after my purchase and I saw an engraving on the cylinder? It said 558 on it I am led to believe that it is a Polaris

558 cc could this be possible? Are there any special companies that bore predators? Also when i am in neutral and i rev it a little bit it sounds fine until it is almost back to idol and there is a funny rattling sound does anyone know what this could be?