1981 GSX1100 Katana Based Project

[Shin-Ken 1074]

The GSX-R 1000 rear master cylinder is now complete after installing a new piston and seal kit and giving it a tidy up. No weight change for it at this stage. Later on I will make an aluminium clevis and pin for it that will shave a few grams off.

master 21 by Max Mutarn, on Flickr

[Shin-Ken 1074]

The rear caliper kit didn't arrive as planned, it has been placed on back-order and should be here by 24th Feb. Looks like I may have time to make that aluminium clevis after all.

[Shin-Ken 1074]

With a few hours to burn I have started making the aluminium rear brake pivot clevis to replace the OEM steel clevis.

Had some scrap 25mm x 25mm ally square bar so that will become the pivot clevis.

clevis 1 by Max Mutarn, on Flickr


Clevis 2 by Max Mutarn, on Flickr


Clevis 3 by Max Mutarn, on Flickr

[Shin-Ken 1074]

The 25 x 25 square ally is oversize for the clevis so its cutting and filing time.


Clevis 5 by Max Mutarn, on Flickr


Clevis 6 by Max Mutarn, on Flickr


Clevis 7 by Max Mutarn, on Flickr


Clevis 8 by Max Mutarn, on Flickr

Basic shape is now done and it fits the brake pivot arm. Some filing and sanding to do as well as drill the pin hole. Should be close to 11 grams when its finished.

[Shin-Ken 1074]

Made the clevis pin from a 6mm aluminium allen bolt.

Clevis pin by Max Mutarn, on Flickr

[Shin-Ken 1074]

The aluminium brake pivot clevis is finished and have test fitted it to ensure all is well. Came in at less than half the weight of the OEM steel clevis so turned out pretty good weight wise. Also swapped the master cylinder threaded adjuster rod from steel to titanium, swapped the steel lock-nut for a nylon lock-nut and swapped the steel clevis pin for an aluminium pin to shave a few more grams off.

Clevis 11 by Max Mutarn, on Flickr


Clevis 12 by Max Mutarn, on Flickr


Clevis 13 by Max Mutarn, on Flickr


Clevis 14 by Max Mutarn, on Flickr

Running tally = 184,419 grams.

[Shin-Ken 1074]

The clevis shape just didn't look right, reshaped it and Iam happy with it now, and 10% lighter.

Clevis 15 by Max Mutarn, on Flickr

Running tally = 184,418 grams.

[Shin-Ken 1074]

Rear caliper kit has arrived from Suzuki, happy days. Flickr is off line right now so pics later today maybe?

[Shin-Ken 1074]

Flickr is back on-line.

Caliper r1 by Max Mutarn, on Flickr


Caliper r2 by Max Mutarn, on Flickr

[Shin-Ken 1074]

As a used caliper I want to know what I have and be confident of it being safe to use so an overhaul is the name of the game today. Bought a Suzuki rebuild kit so it's time to get the job done.

After splitting the caliper cases I weighed the OEM steel allen bolts that secure the cases together.
Caliper r4 by Max Mutarn, on Flickr


As luck would have it there were two titanium flanged M10 x 45 mm bolts in the spares bin that are the exact size to replace the OEM bolts.
Caliper r3 by Max Mutarn, on Flickr


Running tally = 184,379 grams.

[Shin-Ken 1074]

Popped the pistons the usual way with compressed air and a rag between the pistons to prevent damage. The rear caliper is an opposed piston system so I prefer to leave the caliper whole to pop the first piston out.

Caliper r13 by Max Mutarn, on Flickr




Caliper r14 by Max Mutarn, on Flickr


With the first piston out I split the caliper cases and pop out the second piston with air via the brake fluid gallery in the caliper case. A very pleasant surprise inside the caliper, no contaminated brake fluid and no bore damage or pitting.

Caliper r12 by Max Mutarn, on Flickr

[Shin-Ken 1074]

After removing the piston seals, the outer piston seal groove had a small amount of gunge in it so I cleaned the groove with acetone on hand paper.

Caliper r11 by Max Mutarn, on Flickr




Caliper r10 by Max Mutarn, on FlickrCaliper r10 by Max Mutarn, on Flickr

Caliper r9 by Max Mutarn, on Flickr


Caliper r8 by Max Mutarn, on Flickr


Caliper r7 by Max Mutarn, on Flickr

[Shin-Ken 1074]

New seals installed, a smear of brake fluid on the seals, pistons and bore and slide in the new pistons.

Caliper r6 by Max Mutarn, on Flickr


Caliper r16 by Max Mutarn, on Flickr


Caliper r15 by Max Mutarn, on Flickr


Caliper r5 by Max Mutarn, on Flickr

Then install the cross galley brake fluid seal.

Caliper r17 by Max Mutarn, on Flickr

New pads should arrive in a few days.

[Shin-Ken 1074]

Once the new pads are installed and the overhauled rear brake system and new hose is fitted that's another job done. I have been tinkering with the rear master cylinder over the last week and shaved a few more grams from it. Has a few grams here and a few grams there made a difference, yep.


OEM SZ rear master cylinder.
SZ OEM rear master by Max Mutarn, on Flickr


Modified GSX-R1000 rear master cylinder.
Mod master by Max Mutarn, on Flickr

433 grams vs 202 grams is a good result and well worth the effort to reduce the master cylinder weight by more than 50%.

[Lorenzo]

...[there were two titanium flanged M10 x 45 mm bolts in the spares bin]...

"spares bin", gotta be the metaphor of the week