Sourcing the GSXR1000K1 calipers is best done from the USA. The weather there is much better and you generally find the inside faces of the caliper body and the pistons and seals to be in much better condition than on a brake donated from a UK machine of comparable age. eBay is ideal for this and you should be able to get a pair of these brakes for between $75 to $150 depending on the seller. You will almost certainly have to clean them up before installation but, with the brake dust removed, a US sourced caliper is always likely to be in superior condition mechanically.
The original hose arrangement on the ZZR1100 comprised a single hose from the master cylinder reservoir to a junction mounted on the bottom yoke. This then divided the fluid routing into separate hoses to each front caliper. There are small performance loses through this arrangement and the best way to install your new brakes is to replace the hoses with two single lines emanating from the master cylinder off a double banjo bolt, straight to each caliper. Braided hoses will also improve the mechanical efficiency of the setup and do better Justice to your new installation.
The aforementioned procedures represent an upgrade to the original setup. They are not mandatory though and you can just use your whole existing system as is, with the GSXR1000K1 calipers, if you are on a tighter budget. Whichever route you choose, you need to remove the OEM four piston calipers off both hoses. Once you are ready to install the replacement six piston units you need to install an adaptor sleeve in each caliper mounting hole on the fork legs. The sleeve requires to reduce the internal diameter of the fork mount from 10mm to 8mm to take a bolt that will fit the female threads on the replacement GSXR caliper. These calipers also require 1.5 to 2mm of shimming to align them properly with the brake disk and an adaptor sleeve with a flange can perform this function too. An alternative to the sleeve is to use a 10mm shoulder bolt with an 8mm thread and a washer to shim the caliper centreline into alignment. This is an aesthetically less pleasing solution and slightly more fiddly to install.
With the adaptor sleeves insitu you can offer the caliper up to the fork and bolt it up by using two M8×40 bolts through the forks and sleeves into each caliper (to the torque specified for the OEM installation). All that remains is to connect your existing or replacement hoses to the calipers and bleed the system. There is a brief information page and installation video on this which may be helpful.
Happy braking.
