Just bought used 250 chinese buggy it has sat for 2 year . It will start and run but stall any time it is below 1/8 throttle . I have drained and flushed the fuel tank , replaced the spark plugs , removed carb and cleaned out jets and blew out all passageways with carb cleaner . The plug is black when you remove it . The engine runs slightly rough and you can hear it misfire slightly .

 

running pretty rich then if the spark plug is black with carbon/soot, that carb needs to be adjusted. refer to the sticky thread for adjustment. as far as idling, either the idle screw passage is plugged or closed, or the idle jet still has an obstruction and not feeding enough gasoline to the cylinder. you really need to investigate those 2 items.