The adjustments only affect the slow idle. High speed mixture is controlled by fixed jets (orifice plugs) that can be removed and cleaned without taking the carburetor apart.
Are you positive it is a carburetor problem? Don't be fooled by something else.
However if it definitly is a carburetor problem, you are in trouble. Parts and repair kits are pretty much obsolete and may cost more than the whole motor is worth. Don't even think of taking it apart without at least a complete set of gaskets. They are very complex and would be a real challenge to make.
Special tools are needed to remove the high speed orifice plugs and to set the floats. I assume your manual tells you that.