I had this problem on a different scooter (honda dio). I found that the exhaust was fouled up with carbon. Try de-carbonising the exhaust. A temporary fix I found was to stick thin wire back through the end of the exhaust and push it back and forth to break up the carbon.
Scott, September 2007
likely to be water in the fuel tank and or carb or blocked jet or possibly a faulty fuel tap
adam, February 2006
it sounds like you have a fuel problem,remove the carb and clean out the main jet, if the bike ticks over but wont rev then the slow running jet should be clear
