I recently picked up a ransomes bobcat xm3653, it was definitely in rough shape but overall in usable condition and cost me next to nothing. I believe they came standard with a kawi fb460v, but this unit is sporting a kohler command pro 15hp. I noticed after reqching temp it starts to surge, regardless of where you put the throttle and backfires when throttling down. I emptied the tank and changed fuel filter as well as the plug. Still more of the same, I notice now that the little arm coming off of the throttle is moving back and forth on its own with the surge, any ideas?