Trying to fit a spoked front wheel in place of the mag wheel on my 01 1200xls - spoked wheel is a half inch narrower on the centre hub, do I need spacers for the twin discs as well as the hub to compensate ?

Apologies* discs meaning rotors - both wheels are set up for twin discs/rotors, spoked is an inch less wide than the original mag wheel...

 

Helo old chap, from not far North of you! Sounds as if you have an unsuitable spoked wheel, as for a direct swap the two hubs should be the same width. Are they the same width over the disc mounting faces? If not, you are not going to readily make the 'new' wheel work. You need a wheel from the same era as your bike. You can check specs and part numbers on-line here.

 

Ditch the front brake and use spacers