Needle Jet Removal VM20

[Dale]

Mike,
The pin on the top of the cap is just to adjust the idle speed. It serves the same function as the Idle Screw found on the sides of the later model carburetors. So there are two adjustments on the top of the cap. The left side adjusts the slack out of the throttle cable. The right side adjusts your idle speed by raising the throttle slide slightly.

As for your needle jet rotating, there is a pin in the carburetor body and the needle jet has a groove. It should only go in one way. So if it is rotating, then perhaps the pin is either damaged or hopefully the pin has just backed out. The C shape (I call that the shroud) should be positioned so that the opening faces the engine.
Dale