That little black lever (with spring) is hooked to a rod that runs through the lower end. The end of the rod has a cup, and a seal that can open, and let all the oil out of the motor - it just shoots out, on the ground. You can do it running down the road or parked. Then you need to add more oil to the oil tank. This is the only way to keep fresh oil in the lower end. We made a special, small seal to go under the spring to help keep oil from working it's way out the topside too . . .
All the cams just have bushings (like a WL, K model or '57 Sportster). The end of the pinion is accessible from the outside of the gear cover. The VLD. Pretty neat lil' engine. They got big-twin power in a WL-type chassis !