On the side of the carburetor, there must be a bronze screw on the base, that is the air regulator. With the engine running, and in even gear, you close it to the right, and turn to the left three half turns. That would be the regulate standard, but you have to feel that the engine is even, give a couple of accelerated to react the carburetor in each adjustment.
Without the filter, you have to see that the fuel is injected, to see that the chopper pump is working.