More power from Kawasaki TH48 engine?
 

Hi,
I need help to get more power from a Kawasaki TH48 engine. It is 48cc and rated 2.2hp. This is such a nice running engine out of the box. I installed it in my 18kgm CamCopter and it could not even hover. It has 1 to 9 ratio and main rotor rpm is around 1000. It just lacks power. I know this engine was specifically produced for weed trimmers and that is probably why it is low powered. Considering the fact that I am in Istanbul-Turkey, can you tell me what modifications can be done on this engine in order to get more hp? (3.5hp or more contnious)
Any help will be appreciated.
Ahmet