You can do anything to these motors. Big bore kits, really big bore kits, camshafts, cylinder porting, bigger carbs....you name it its available. It all depends on what you are looking for as far as performance. There are upgrade ignition system, charging systems, exhaust kits, suspension, etc. Look around Cycle X website and you will get a very good idea what is available and what can be done with these bikes and motors. Tell us what you are looking at doing to you bike and will give you suggestions and opinions and experience with them.