My brother's 650 is running badly. He replaced the spark plugs, emptied the gas tank and put in fresh gas. One day it runs fairly well and the next day not so good. I would guess its a partially plugged fuel filter. Does this 650 have a fuel filter? Also, he says the fan doesn't come on but since he rides the city streets mostly, it probably doesn't need to come on. Were not sure it even has a fan. We are not exactly mechanics. Any thoughts on what needs to be done!