My Murray walk behind all the sudden does the have any RPM, just idle. It is a B&S,12F702-0714 engine. I changed fuel, filter ,plug rebuilt carb, still when it starts just an idle. I can manually open throttle and it runs up. I have noticed the after it starts the throttle is near or at the start position. I,m beginning to think there is a spring gone, presently there is the linkage to the crankcase Governor and one to the throttle arm. Small engine parts warehouse suggest by there carburetor parts list there might be a third part. I ordered all three but do not have a clue where or how it would hook up Thanks. My first time out.