When checking these types of generator capacitor, i use a known good one in its place. The actual capacitor value must be the same, as a different value changes the generators voltage.
Update , took the Capacitor to a company that repairs generators , they said wasn't worth paying to have it looked at but tested the Capacitor and said it did not need replacing , was working perfectly and within tolerances . Back to the drawing board because i cant think what else it could be and the cost of a step down transformer is out of the question would be a shame to throw the whole thing away as its like new and had such little use .