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A Blade Reforged: SUZUKI GSX1100S KATANA Custom by Custom Factory Katanakaji

 16 min read

Custom Factory Katanakaji's GSX1100S KATANA

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"We've made some changes this time around. The frame was rebuilt, the exterior was replaced, and the controls were also upgraded. These changes all worked and meshed well together, and we were able to achieve a third place result and a lap time in the 58-second range (58.972 seconds)," said Mr. Ishii of Custom Factory Katanakaji.

This bike consists of an oil-cooled engine loaded into an original frame combined with the looks of the GSX1100S. It was built to compete in the Hercules class of the Taste of Tsukuba (TOT), a race held at Tsukuba Circuit, and has been competing since 2014 under the name "The Sword". The third place rank and 58-second lap time were achieved at the TOT SATSUKI STAGE on May 14, 2023, and were the best results so far for this machine. Just what kind of changes were made? Let's take a look at the details.

"The frame was originally made based on the dimensions of the GSX-R1000 K5. Our rider told us that it felt as if he were being pushed from the rear. It had the right amount of rigidity and bend, but when a big force was applied, it felt like there was no place for that force to escape. So we changed from a box to a pipe & plate structure so as to reduce the rigidity of the upper mount of the rear shock, which is a mono suspension. And from a structural standpoint the rear engine mount and seat rail also had to be rebuilt," said Ishii.

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Originally, in the last race (November '22), the rider had not felt the feeling of being pushed from the rear, and when Ishii investigated, he found that there was a crack in the shock mount. This actually gave him the hint he needed and worked out for the better. We also asked about the oil-cooled engine that has been converted to 1277cc and is now consistently producing 160 hp and 13 kgf-m of torque.

"We added an oil cooler for the head. The oil line for the head has been independent until now, but we sandwiched the oil cooler on top of this line, and it really cools. I was sure it would, but I was surprised when it didn't even get up to 100 degrees (Celsius)," says Ishii.

The oil from the oil pump is cooled by the main oil cooler placed in front of the engine before flowing to the various parts. The oil that goes to the head is passed through an additional oil cooler placed inside the cowl, cooled further, and then returned to the oil pan via the original oil collection channel. This engine is capable of producing 170 hp, and Ishii's idea was to provide more heat protection to ensure stable output of that high power. In fact, there was some extra ingenuity that went into the additional oil cooler.

"We placed the cooler inside the front cowl, where wind hits the hardest. The fins under the cowl are also a new addition, and they are shaped in such a way that air is drawn into the front ducts and out the back as well. Though we also put them there for the fashion aspect,” Ishii commented while laughing.

For the exterior, the seat has been changed so that it has no side covers. The step position was also lowered to increase freedom of ride position. In addition, the clutch was also changed from the standard oil-cooled hydraulic type to a wire type.

"In '21 and '22, when racing, there were many cases of bubbles appearing in the piston part of the clutch release due to slight vibrations, causing the clutch to suddenly fail to disengage. We heard that this was one of the reasons why supersport bikes on the market had switched to the wire type, so we made this change in response to a request from our rider for a more direct feel in operation. But the operation itself is heavy, and if you are just riding around town, you won't have this problem, so a hydraulic clutch with lighter operation is fine,” said Ishii.

The increased power is stable to the end, unintentional movement of the bike body is eliminated, and there is an increase in the freedom of operation. These effects all worked together to produce the race result mentioned at the beginning of this article.

"We are still in the middle of our journey with this bike. Now that we have achieved good results, we can think about the next plan for further improvement. The body itself is looking good, so now we can put our efforts into other parts and test those out. For the next race, we are thinking about changing the exhaust and planning some other upgrades as well,” says Ishii, who already has his sights set on the next soup-up plan for this oil-cooled machine. We look forward to seeing the next version of this custom, which has given us high expectations for both oil-cooled bikes and the KATANA form.

Handle

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The front master cylinder is Brembo and the handlebars and lever guards are by BABYFACE. The meters include a Yoshimura PRO-GRESS and a tachometer made by Scitsu, a brand that KATANAKAJI offers.

Bodyworks

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The aluminum cowl bracket at the front end of the frame was reshaped, and an additional oil cooler for cooling the cylinder head is installed inside the front cowl.

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New ducts were added under the front cowl, and carbon fins inspired by the KATANA look were added on both sides. The number plate was also reshaped, especially at the lower end, to efficiently direct air into the ducts along with the added fins. The fins also serve to vent the hot air that has passed through the cooler.

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The front cowl, tank cover, seat cowl, and other exterior parts are made by Magical Racing, and the seat has been reshaped to remove the side covers.

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The frame is made of steel pipe (with plates in some places). The seat rail is made of aluminum, and was created by KATANAKAJI to match the rear cowl modification.

Engine

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In 2018, the engine was increased from 1156cc to 1277cc, and the specifications generally remain the same as at that time. The cylinder is a GSF1200 with 2 valves and 1 rocker arm head, and the crankcase/crankshaft is from an '89 GSX-R1100(K). The pistons are forged JE φ83mm, the connecting rods are Carrillo, and the cams are Yoshimura ST-2, with inner stud collars and filling around the studs to prevent heat distortion. These specifications are designed to stably produce 160ps or more. The transmission used to be a 6-speed made by KATANAKAJI, but there was no replacement for it, so a TG-RUN 5-speed cross transmission was used this time. Mr. Ishii is happy with the ratio, which is suited to the conditions of the TOT race.

Intake & Exhaust

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The carburetor is a TMR φ40mm, and the exhaust is a J-CUSTOM Titanium 4-1. The cylinder head cover is now finished in red, and a line to the additional oil cooler has been added. This line sends oil from the oil filter to the additional cooler and then to the head.

Chassis

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The steps are made by BABYFACE, and the step bar position has been lowered in accordance with the seat change to improve control.

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The frame was made by KATANAKAJI. The upper mount for the shock was changed, as seen in the photo. Originally a box structure, it was rebuilt with a pipe and plate structure to prevent unintentional movement of the rear and stabilize the body. As a result, the rear engine mount and many other related parts were also redesigned.

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View of the new shock upper mount from the right side. The shock upper mount is designed to allow for setup of the shock at full length.

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The front forks are Ohlins FG RT inverted for the GSX-R1000 with a stem also compatible with the GSX-R1000. The front brakes are composed of Brembo CNC racing calipers and SUNSTAR Works Expand discs, with Magical Racing caliper ducts added to stabilize their effectiveness.

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The swingarm is from a GSX-R1000, the rear shock is an Ohlins TTX, and the rear brakes use a Brembo CNC racing caliper and SUNSTAR Works Expand disc. The wheels are BST Carbon "Diamond Tek" 3.50-17/6.00-17. The drive chain is a D.I.D 520ERV7 for race use, and the rear sprocket is by X.A.M.

Gallery

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Specifications

Part Details
Engine JE PISTONS Piston Kit
YOSHIMURA Camshaft [ST-2]
TG-RUN 5-SPEED Cross Transmission for SUZUKI Oil-cooled Engine
CARRILLO Special Connecting Rod
KATANAKAJI Engine Slider
KATANAKAJI Original TSS Slipper Clutch
KATANAKAJI Oil Catch Tank
TERAMOTO T-REV Pressure Reducing System
Carb / Intake Mikuni Model-Specific TMR Carburetor Kit
Exhaust J-CUSTOM Titanium 4-1 Exhaust
Brake brembo Racing Radial Brake Master Cylinder
brembo Racing Radial CNC 4P Caliper
SUNSTAR WORKS EXPAND Front Disc Rotor
Magical Racing Caliper Cooling Duct
brembo Racing 2P Rear Caliper
SUNSTAR WORKS EXPAND Rear Disc Rotor
Wheels BST DIAMOND TEK 3.50-17 Front Wheel
BST DIAMOND TEK 6.00-17 Rear Wheel
Suspension OHLINS Upside Down Front Fork FG R&T 200
OHLINS Rear Suspension TTX-GP 2018
Steps KATANAKAJI Original Step
Drive System D.I.D 520ERV7 Drive Chain
Handle / Steering BABYFACE (Sato Racing) Race Concept Handlebar Kit
BABYFACE (Sato Racing) [Race Concept] Lever Guard Set
Scitsu Tachometer
YOSHIMURA PRO-GRESS2 Multi-temp Meter
Bodyworks Magical Racing Carbon Front Fender
Magical Racing Carbon Upper Cowl
Magical Racing Windshield Base
Magical Racing Windshield
Magical Racing Tank Cover
Magical Racing One-Off Seat Cowl

Original Source of this Article

Heritage & Legends

Hakuyo
Hakuyo

editor

Hakuyo

A foreigner who rides in Japan, Japanese call this "Gaijin Rider". Third year in the Webike global team. He feels and shares the real bike life in Japan then presents you how interesting Japanese customs are.