You'll need a 5 way 4 pole switch either from all parts or the original yamaha switch.
The schematic can be found here: http://www.geocities.jp/dgb_studio/2hvari_e.htm#148
It's a simple but proper electronics schematic which dumbfounds even the most reputable 'wiring gurus' so take your time to draw it out pictorially. A multimeter would certainly be useful.
KC