I had the 790cc,when I bought it new they told me it had 62hp,I got it dyno'd after I got the carbs and exhaust done and it said it was puttin out 62hp.Ithink the 865 is suposto put out 55hp stock.Inow have a904 kit in one and it dyno's out at 75hp.You will gain somthing with the k&n,carbs and new exhuast.
