When i bought my MC21 I also got a HRC wiring loom. Read about the ignition restriction and thought that the HRC loom would solve the problem. This is what i did without really understanding what exactly this "hrc box" does. (look at the pic)

http://goldwing.bikepics.net/honda-nsr250-90-bikepics-057322.jpg

It worked, since the bike started, but it didnt really make a difference that I could notice.

@ Dave Ett: Is this what you mean by "adapt the cables to suit"?
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MC21, GP-Replica (Daijiro Kato, Telefonica Movistar Team 2001)