Shifty, are you saying that the fuel suction pipe is clear, but you still can't get it to run rich by turning the mixture screw anticlockwise? Remember there is a non-return valve in that pipe, as well as the screen on the lower end. Be sure the valve is clear, in case someone has "cleaned" the filter at some point by pushing the crud through it into the non-return valve.
Compressed air will not clear the passages in a carburetor. You have to use solvent if you need to clear the passages (which is seldom necessary, because of the fine screen on the bottom of the suction tube). The compressed air is just to blow the solvent out, to get rid of it after it has done its job. On its own, the air will just blow the crud into the wrong places and pack it hard.
I think getting the cylinder and bedknife sharpened by a proper expert typically costs $50-70. However it is essential that the bedknife is included: you can't mow properly with a blunt or wavy bedknife.
When you have the governor working properly you can make a reasonable check of whether the mixture is actually lean by running the engine at maximum speed and putting a reasonable load on it. It is fairly sure to hunt (cycle in speed every second or two) if it is lean. It can be difficult to check by using the kind of choke you have. Also, remember that you can only test mixture with the air cleaner fitted, including its retaining screw in the center of the carburetor intake.
