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CBR900 Nissin 4-piston caliper information needed

Old 06-15-2011, 06:21 AM
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CBR900 Nissin 4-piston caliper information needed

I am doing a brake caliper conversion using some Nissin brake calipers and master cylinder from what was listed as a CBR900. Got a great buy on ebay - $32 for the whole shooting match. Now I know there were several versions that might qualify under the 900 listing. I know there are some differences in piston sizes of both the calipers and master cylinders.

What I have a question about is the caliper breakdown. It appears I could do well to install my carrier plate bolted on from the inside, which requires I either grind the inner caliper casting or take it apart and bolt the plate on in a mostly permanent way. In other words once the bracket is bolted on it will not be removed in the forseeable future. Caliper removal will be done unbolting the carrier at the fork.

I realize the caliper requires some specific torx socket to split it. What I am asking is this:
  • What is the torx head size?
  • How much of a headache is it to take apart the caliper
  • Is there any more to deal with than a few O-rings inside?
  • Is there any suggestion on cleaning and prepping for reassembly?
  • I also need a source for the torque spec for the fasteners on reassembly.
Once I get things apart I can see what caliper piston sizes are.
  • Is there any marking on the master cylinder that gives hint of the piston size in it?
I'm open to any tips and suggestions here.

I'm going from the twin piston Zephyr brakes to the CBR brakes and figure possibly some of you have experience with them. I'm hoping for some serious hard stoppers here. It is also a bit of a fore runner test to making conversion kits for Eliminators per a request by one of the guys riding them. Probably use the Tokico 4-piston brakes from Ninjas since they seem less expensive and reasonably plentiful. They also use the same MC size piston as the Eliminator used.
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Old 06-15-2011, 06:48 AM
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There's a lot of very helpful information under the title "List of Bolt-On Front Brake Mods?????? " in the Modifications - Performance section.
You're dealing with calipers which are more than 10 years old and which probably haven't been split. What you see when you split them may not be pretty.
I don't know if the bolts have Loctite on them or not but heating the caliper before I attempted to remove the bolts helped me. Sorry, I don't know what size the torx bit is. Take a caliper when you go shopping for a torx bit.
The insides are pretty simple. There are two seals per piston and an O-ring type seal for the passages between the caliper halves. It shouldn't be hard to find a parts microfiche for a 900RR to give you a clear picture.
You may be able to reuse the original seals but replacing them is probably a better idea. I don't think that there's a rebuild kit available and you may be have to buy seals individually but I stand to be corrected.
You've got to be sure the grooves that hold the piston seals are spotless. Otherwise, the brake pistons may not retract sufficiently.
I use a metal polish such as Solvol Autosol to clean pistons if a toothbrush and brake fluid aren't enough.
I just used the torque spec from the VTR shop manual. The bolts are the same IIRC.
I would not use the original brake lines. They will have deteriorated.
Vesrah RJL pads are a good way to go.
Hope this helps. I'm sure others will chime in
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Old 06-15-2011, 10:38 AM
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AFAIK, the 92-97 900RR calipers are essentially the same as the VTR`s (27/30mm piston sizes, identifiable by their more angualr shape). The 98-99 calipers are extrenally similar to those used on the F4i, 929, 954, RC51 and early (non-radial) 600RR. These have (along with the SP-1 and F4i) the largest piston combo, that is 34/32mm. To mount them to stock VTR forks, a slight bit of grinding will be required. From experience, having run 98 900RR calipers on my VTR for a few eyars (and now mechanically identical F4i units), I suggest you invest in a radial MC (Nissins can be had relatively cheap on eBay). Get steel lines, decent pads (RJLs work well) and you`ll be very happy with the stopping power.
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