Hangar 9 J-3 Piper Cub Assembly Manual page 27

Section 10: Assembling and Installing the Fuel Tank
6. Install the open tube end of the clunk and tubing
assembly on the short copper tubing.
7. Press the 3mm nut between the three pegs on the inside
white plastic cap as shown.
8. Carefully insert the assembly into the fuel tank. Note the
position of the vent tube. It must be at the top of the fuel
tank to function properly.
fuel tank
pickup tube
vent tube
9. Insert a 3mm screw into the center hole of the stopper
and tighten.
Important: Remember which tube is the fuel pickup and which
is the vent so that you can properly connect the fuel tank
to the engine.
10. Note that the fuel stopper is mounted closer to one edge
of the tank than the other. This "closer edge" is the top of
the tank. Slide the tank into the fuselage stopper first.
Make sure that the top of the tank is positioned toward
the top of the fuselage.
11. Press the tank into position until the stopper inserts into
the hole in the firewall.
12. Plumb the fuel tank and the engine accordingly.
Connect the vent tube from the fuel tank to the muffler
pressure fitting. The remaining tube should be attached
to the carburetor fitting.
CONTINUED
27