Power in an IC engine will be limited by restricting fuel flow or restricting airflow or both. When you say "...doesn"t have any power." does that mean you put the tractor under load and it stalls? If so then check the following
Start with the easy part. disconnect the air filter from the carb intake (short hose). DO THIS ONLY IN AN AREA WHERE IT IS NOT DUSTY! Usually the air filter will not be a problem unless you are demanding full power output from the engine( i.e. plowing in heavy soils).
Next make sure you have adequate fuel delivery from the tank outlet to the carb fuel bowl. There is a filter in the sediment bowl a the tank outlet make sure it is not restricted. There is a "secret filter" at the carb inlet fuel elbow. Make sure it is not blocked. Check the fuel line for pinched fuel line.
Poor spark will limit power as will incorrect engine initial timing and a failed centrifugal advance mechanism in the distributor.
Systematically check all these before you consider messing with the governor.