As Deejay said Top, we need the Model, Type and Code to sort out the engine properly. Meanwhile, the way the governor works is quite simple. Inside the crankcase there is a simple device that spins at engine speed and has centrifugal weights on it. The weights push on a paddle connected to the shaft that governor arm mounts on. The faster the engine spins, the harder the weights try to rotate the governor arm shaft, and thus move the end of the governor arm that is linked to the engine's throttle. The governor arm is pushed toward closing the throttle by that centrifugal mechanism, and it is pulled the other way by the governor spring. The amount of tension on the governor spring is set by the speed control lever on the side of the engine. So, the engine runs with a balance of forces on the throttle: the centrifugal mechanism trying to close it, and the spring trying to open it. If the governor arm is loose on its shaft, the centrifugal mechanism can't push the throttle toward the closed position, but the spring can still pull it toward the open position.
You usually adjust the position of the governor arm on the shaft coming out of the engine by rotating the shaft clockwise as far as it will go, while pulling the arm clockwise as far as it will go (toward full throttle), then tightening the clamp bolt while everything is held in that position. However we need to check how it is done exactly, for your specific engine, by looking in the workshop manual. To do that we need the Model, Type and Code.
