kymco super 9s keeps loosing power anyone help

[kevemo]

hi all
   my nephew has one of these on an 05 plate  it starts fine and runs fine but has an intermitent fault it will be going fine then out of the blue just seems to lose power if he stops turns it off and then restarts it it will run fine again.
have put a new coil on it emptied all petrol out and put fresh fuel in had carb apart all seems fine so now stumped
                                  any help would be much appreciated

[zombie]

Sounds like dirt in the fuel system somewhere. Try a new filter. Also my zx did the same thing. If i shut down for a coup. hours it would run fine for 10 -20 minutes, until i changed the cdi. that was my problem.