DO NOT tamper with the air gaps! The spring tension on the voltage regulator coil points is too high. With the engine running at a fast idle, (1500 RPM or so), the voltage should be approximately 7.5 volts against a fully-charged battery. The voltage regulator coil is directly behind the "F" wire connection, so if there is a screwdriver adjustment on the point spring, reduce the tension slightly, open the points for a couple of seconds by pushing on the movable point, and check the voltage at the "Bat" terminal when the cutout relay recloses. If the spring arm is tensioned by a tab without a screw adjustment, bend the arm slightly up or down to change the voltage setting. CAREFUL! A tiny change in spring tension makes a big voltage change! The voltage setting will drop slightly when the cover is put on the regulator because steel conducts magnetism better than air, so adjust the voltage about 0.1 or 0.2 volts higher than you intend to have when everything is buttoned up.
Jerry