Hi,
Think the R1 has different spaces between the mounting bolts so it doesn't fit... using the search function might throw up the threads that mention it.
To fit the R1 caliper would require a different caliper mounting plate which could in turn throw out the space for the rear wheel or not fit the rear axle spindle.
If you think you can make it work then go for it, the fazer thou calipers are harder to find than an Essex virgin...
The trx 850 rear caliper and mounting bracket fit without any mods too.
Chris