K1 - Brake Mods
Tokiko 6 pot brakes from a GSXR1000K1/2 (March 2003):

This modification applies to all J, K, L and M models.
The brakes on all ZXRs are very good already, yet it had begun to bother me that the 6 pots on my P model ZX7R were both more powerful and more progressive than the 4 pots the ZXR750R is equipped with. I begun to look for alternatives, but the P model ZX7R brakes don't fit, Harrison billet calipers are something like £540 (GBP), AP and PFM don't list an upgrade for it and the price is colossal anyway. Then I noticed that the caliper mounts on Suzuki's GSXR1000 (K1/K2) looked very similar to the ZXR's. I took some measurements and decided that was the way to go.
Buying a set of new calipers from suzuki proved more expensive than Nissin and Harrison so I resorted to the breakers and 24hrs later I was the owner of a set of nearly new gold Tokiko 6 pot calipers. I cleaned them and greased them up and they were like new.
Mind you they are not a straight fit. The mounting points have the same spacing and they fit the standard ZXR rims, however you need to use new mounting bolts (as the ZXR uses M10s and the new calipers want M8s and the Suzuki bolts are not long enough) and specially made spacers (easily made by any machine shop). The spacers have two functions: A) they narrow down the caliper mounting holes on the forks from 10mm to 8mm to suit the new bolt and B) most importantly, the spacer's collar allows to get the caliper spacing right by positioning the middle of the caliper exactly over the middle of the disk
IMPORTANT NOTE: Calipers are a stressed area hence make sure that you use high tensile steel caliper mounting bolts or better still titanium grade 5 ones.

This is what you need: Pair of GSXR1000 (K1/K2) calipers x4 High tensile steel bolts M8x35 or Grade 5 Titanium bolts (1.25 thread) x4 Steel spacers (specially made - see diagram): body length:19.5mm body external diameter: 10mm body internal diameter: 8mm collar diameter: 16mm collar thickness: 1.5mm total length: 21mm Brake cleaning fluid Hi Temp Caliper grease Dot 4 or higher brake fluid New washers for the banjo fittings Brake bleeding kit New Brake pads

Spacer

1. The caliper are likely to be fairly new hence you probably will only need to clean them thoroughly rather than strip and rebuild them.

2. If you are not stripping the calipers keep the banjo bolt holes plugged whilst you clean the calipers to avoid dirt getting inside the calipers. An old toothbrush and some brake cleaning aerosol should do the trick.
3. Put piece of wood between the pistons (about 20mm thick) and use a footpump with a nozzle to push the pistons further out of the seals so you can clean them properly (if you get them out completely you will have to dismantle the caliper to fit them back in).
4. Grease the pistons and push them back in.
5. Fit the spacers in the mounting holes in the forks with the collars on the inside of the fork i.e. facing the wheel (in the picture the spacer is slighlty pushed out of the hole to better show hot it is fitted).
   
6. Now fit the calipers remembering that the tightening torque for these calipers is only 18ft/lbs!!!

PLEASE NOTE: If you use Titanium bolts make sure you lubricate the threads with something like Moly or Copper grease otherwise you could experience "cold weld" (over time titanium can weld itself to the surrounding material). Very very bad as titanium is next to impossible to drill out.

IMPORTANT NOTE: Make sure the bolt heads are at leat 12mm in diameter (preferably larger). If in doubt use a suitable steel washer (1mm thick max) under each bolt)
7. Connect the hoses.
8. Make sure the disks are well degreased.
9. Grease the pad retaining rod and fit the pads (MAKE SURE YOU GET NO GREASE OR BRAKE FLUID ON THE PADS!!!).
10. Cover the tank and any exposed area to avoid spilling dot4 on your paintwork (it's a good paint stripper).
11. Fill the brake fluid reservoir and follow the instructions of your brake bleeding kit to thoroughly bleed your brakes
12. Have a gentle run to test that everything is working OK. Give the pads time to bed in and then enjoy!

Interesting Facts:
The GSXR1000 calipers are nearly identical in construction to the 6 pots of the '96 on P model ZX7R and they take the same pads. However they are considerably lighter at about 830g each (without pads) against 1020g. Also the coating on the pistons looks far less likely to suffer from pitting (good for us in the UK).
The ZXR's stock 4 pot brakes weigh 1310g each (with brake pads and caliper mounting bolts. The new 6 pot gold Tokikos weigh 1210g each (that's with Brake pads, Titanium mounting bolts and steel spacers). It all adds up to a net saving of 100g each so a saving of 200g of unsprung weight!!!. They also look 300 times cooler than the previous 4 pots.
The above spacers will allow you to mount not just the GSXR stock calipers, but any caliper that fits a GSXR1000. Beware though if you want to upgrade the disca the GSXR items won't fit. Use those for a '96 up P model ZX7R instead.

Disk Upgrades: I have not upgraded my discs, however a point worth mentioning is that If you plan to upgrade the discs and have also done the above modification then go for discs to suit a P model. This is because, though the standard discs work fine, the P model ones have a slightly narrower track to suit the 6 pot calipers hence the brakes will bite the same surface, but the rotors should be lighter and they should fit straight in. Having said that EBC for one don't make a distinction and use the same part for all models from '91 to today.