SpeedyManiac said:
Buy a bigger bike. Seriously, increasing the power of a 230 is only going to show its other weaknesses (frame, suspension, etc) more.
Truer words were never spoken. Either of the 230's can be made to have near 26-28 hp if you know what your doing. I agree with Rich, Frank can build this motor to this level with a 250cc kit, porting, cam, carb, and exhaust.
Your words indicate that you do not have the cubic $$$ to do this properly. There is a reason that there are many, many 8-10 K mini's running around. That is an honest investment level if you want all things to work together (chassis, brakes, suspension, motor, etc)
I know this sounds harsh, but it is reality. If you overpower the chassis/suspension it will end up costing you physically (injuries).
If you do not have the sheckles, accept it for what it is or look elsewhere. I suggest that you sell the 230 and buy a used 125 for the same money, unless you are willing to invest what it will take for the 230...if you must have more.