I have a 873g ser#514142879 When i start it. it wants to move. lap bar up or down it does the same thing. i have to hold the controls handles when i start up. because it starts to jump to one side or the other. if i raise the idle to about half it will stop moving and i can get out of the machine. if I left the idle low it will start to move on its own most of the time it goes to the right. Any idea what my problem can be. I need a starting point.