NT Carb Orings          $1.49
Motorized Bicycle NT Carburetor  O'ring seal

A common problem with these carburators are  Air Leaks
which cause engine failer. Install this Fuel Resistant
Rubber seal between your Carburator and Intake manifold.

Each kit comes with 2 seals.

See our seals installed at this link.  
http://www.youtube.com/watch?v=gk5yl0JOadY