At left are the contents of the Onan carburetor rebuild kit and (#9) the main needle with old bad O-ring still installed and (#10) the float valve seat with the rubber seat still installed. The parts and their applications are listed here:
1=bowl retainer gasket (internal - reuse old outer) 2=intake manifold 3=bowl (reuse old if OK) 4= not used 5= new idle adj. needle 6= new float valve needle 7= new float pin 8= unused 9=main adj. needle - O-ring(#12) goes on it 10= float valve seat (press old rubber seat out and install new one (#13) 11=gasket for under valve seat (#10) 12=O-ring for main adj. needle (#9) 13=float valve seat for #10
At left is a view of the back of the float valve which has a rubber valve seat that must be replaced by pushing it out using a drill bit from the back.
This is the front view of the float valve seat. After the rubber seat has been removed by pushing from the back the new seat and retaining ring (#13 above) are pushed in from this side using a drill bit that is as close to the inside diameter as practical.