As far as I recall you should be able to reverse the engine direction if the part of the crankcase that holds the carb is a separate part held with screws, it needs to be rotated 90 degress CC looking from the front of the engine, but of course this will only work on FRONT CARB engines only, again I could be wrong, you need to validate this, don't know your specific engine, the OS91DF has the carb in the rear so you cannot do it...