The most reasonably priced component used on the Nt400 Bros 1989 (k) Japan Nc25-105 E-18-1 is the Screw,cross,4x10.
A sample from the products for the E-18-1 include: Jet,main(#142), Jet,slow,#35, Valve Set,air Cut, Screw Set C.
The Honda E-18-1 has twenty-seven products enlisted in the schematic.