{"id":2926,"date":"2026-06-20T20:29:40","date_gmt":"2026-06-20T11:29:40","guid":{"rendered":"https:\/\/www.decoboco.info\/en\/?p=2926"},"modified":"2026-09-24T12:54:45","modified_gmt":"2026-09-24T03:54:45","slug":"unicorn-japan-gsx1200s-oil-cooled-katana-rear-brake","status":"publish","type":"post","link":"https:\/\/www.decoboco.info\/en\/20260620\/everyday-events\/unicorn-japan-gsx1200s-oil-cooled-katana-rear-brake","title":{"rendered":"[Maintenance Log] Unicorn JAPAN “Oil-Cooled Katana” GSX1200S! Rear Caliper & Rear Master Overhaul"},"content":{"rendered":"
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I thought I took a photo but didn’t.
The beginning of blurriness? My chicken brain is progressing…

Usually it happens when the phone rings, a LINE message comes in, or a package arrives.
Based on the title classification, I’ll be doing the rear caliper\/master overhaul. <\/p>\n\n\n\n

Today’s Maintenance Log<\/strong><\/span><\/div>
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Vehicle:<\/strong> Unicorn JAPAN GSX1200S “Oil-Cooled Katana”<\/strong>(Based on Inazuma 1200, etc.)<\/p>\n\n\n\n

Work Content:<\/strong> Overhaul (OH) of the rear brake caliper and rear brake master cylinder, fluid replacement. <\/p>\n\n\n\n

Mechanic’s Perspective:<\/strong> A jewel of a complete machine that combines Katana styling with oil-cooled power. Because the performance is so powerful, the condition of the brakes that stop it is absolutely non-negotiable. Following the 1100 Katana from last time, we’ll thoroughly clean and refresh the brake system in the recessed rear area of this oil-cooled Katana with complete seal replacement! <\/p>\n<\/div><\/div>\n\n\n\n

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Another BLOG by Decoboco.
“RURAL GARAGE<\/strong>“<\/span>

A hidden room for non-motorcycle topics.
Sharing everyday convenience items, relocation, delicious food, life philosophy<\/strong>and more. <\/span>
\u2190click<\/span><\/strong><\/p>\n<\/div><\/div>\n\n\n\n

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\n\t\t\t\t\t\n\t\t\t\t\t\tiHouse All Earthquake Gel Extreme Earthquake Mat Adhesive Mat Anti-Slip Washable Vibration Absorption Earthquake Countermeasure Up to Magnitude 7 Load Capacity 100 kg (Clear, 8 Pieces (4 cm \u00d7 4 cm \u00d7 0.5 cm))\t\t\t\t\t<\/a>\n\t\t\t\t<\/div>\n\n\t\t\t\t\t\t\t\t\t
iHouse all<\/div>\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\t\u00a5999\t\t\t\t\t\t\uff082026\/09\/21 12:36\u6642\u70b9 | Amazon\u8abf\u3079\uff09<\/span>\n\t\t\t\t\t<\/div>\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\t\n\t\t\t\t\t\t\t\"\"\n\t\t\t\t\t\t\t\u53e3\u30b3\u30df\u3092\u898b\u308b<\/span>\n\t\t\t\t\t\t<\/a>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t
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\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\n\t\t\t\t\t\tAmazon\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t<\/div>\n\t\t\t\t\t\t\t
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\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\n\t\t\t\t\t\tYahoo!\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\"\"\n\t\t\t\t\t\u30dd\u30c1\u30c3\u30d7<\/span>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t<\/div>\n\n\n\n
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\n\t\t\t\t\t\n\t\t\t\t\t\tSunstar (SUNSTAR) Rear Sprocket 530-45T GSF1200 Inazuma 1200 GS1200SS RS-104-45\t\t\t\t\t<\/a>\n\t\t\t\t<\/div>\n\n\t\t\t\t\t\t\t\t\t
\u30b5\u30f3\u30b9\u30bf\u30fc(SUNSTAR)<\/div>\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\t\u00a515,170\t\t\t\t\t\t\uff082026\/09\/21 12:36\u6642\u70b9 | Amazon\u8abf\u3079\uff09<\/span>\n\t\t\t\t\t<\/div>\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t
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\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\n\t\t\t\t\t\tAmazon\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t<\/div>\n\t\t\t\t\t\t\t
\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\n\t\t\t\t\t\tRakuten\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\n\t\t\t\t\t\tYahoo!\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\"\"\n\t\t\t\t\t\u30dd\u30c1\u30c3\u30d7<\/span>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t<\/div>\n<\/div>\n\n\n\n
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Time passes…and the cleaning is done. <\/h2>\n\n\n\n
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This gem! The GSX-R1000K1\/2 (GS1200SS) is actually an anodized caliper.
So there’s no corrosion around the grooves and the work progresses quickly. <\/p>\n\n\n\n

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We also finish the bleeder that we’re reusing with wet blasting. <\/p>\n\n\n\n

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Rare? To have aluminum piston kits (OEM) in stock is amazing…
The old one will be kept as a stock part. That’s impressive. <\/p>\n\n\n\n

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The pad pins on this rear caliper tend to loosen easily.
It’s a good idea to drill a hole in the pad pin.

Does anyone know if there are pad pins with holes already drilled? <\/p>\n\n\n\n

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That’s how it’s done. <\/p>\n\n\n\n

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The rear pads are on the verge of collapse, so let’s replace them. <\/p>\n\n\n\n

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It’s all titanium, but the lightening holes accumulate dirt as they age.
We cleaned it up nicely with wet blasting. <\/p>\n\n\n\n

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The rear master is NSF100 1\/2<\/h2>\n\n\n\n
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There was no fluid seepage.
The judgment for the rear master: if you remove the boot and find rust, it’s usually a goner.

Actually, it’s a place you should disassemble before that. <\/p>\n\n\n\n

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Quick wet blasting & gun coating for prep\u2014yeah, it really is 1\/2. Fixed with M6.
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Honda doesn’t have the cup assembled, so you need to insert it. <\/p>\n\n\n\n

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If this thin return port gets clogged, the hydraulic pressure stays applied.
Is it a solid lock or a gradual lock?

Don’t underestimate hydraulic brakes\u2014you could get hurt! Hehe (*\u00b4\u03c9\uff40*)<\/p>\n\n\n\n

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Done! The rear master overhaul is complete.
Maintenance really is the most efficient approach (*\u00b4\u03c9\uff40*)<\/p>\n\n\n\n

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Front brake pad replacement & cleaning. <\/h2>\n\n\n\n
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Beta pins (cotter pins) should not be reused once opened.
These small details lead to safety and reliability. <\/p>\n\n\n\n

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Ideally, “pointing upward” should prevent it from falling out.
Let’s increase the chances of safety. <\/p>\n\n\n\n

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We also wet-blasted the reusable parts in this area.
Equipment really matters! Tools really matter! They’re absolutely essential.

To be continued. <\/p>\n\n\n\n

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Rebuilding the Rear Brakes on the Legendary Unicorn JAPAN “Oil-Cooled Katana”<\/span><\/div>
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GSX1200S! Vehicle:<\/strong> GSX1200S Oil-Cooled Katana (Built by Unicorn JAPAN). Topic:<\/strong> Comprehensive overhaul of the rear brake caliper and master cylinder. Details:<\/strong> Following up on our classic 1100 Katana brake job, today we have a very special machine in the Mutsuzawa factory: the GSX1200S “Oil-Cooled Katana,” an absolute masterpiece custom-built by the specialists at Unicorn JAPAN. Because this oil-cooled brute packs serious modern power, the braking system must be flawless. We completely stripped down the rear caliper and master cylinder, which had accumulated road grime and suffered from hardened rubber seals over the years. After deep cleaning the fluid channels, we rebuilt the entire rear setup with fresh OEM seals and pistons. Verdict:<\/strong> The pedal feel is now incredibly responsive and solid, allowing the rider to easily modulate the bike’s massive torque. Preventative maintenance is the key to enjoying classic styling with modern oil-cooled performance!<\/p>\n<\/div><\/div>\n\n\n\n

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