ZRX1200R Spec Engine: GPZ1100 Racer Custom

POWER BUILDER's GPZ1100

The GPZ1100 was built by modifying the frame and engine of the GPZ900R and remaking the chassis. This machine belongs to a racing team of POWER BUILDER. When the GPZ900R starts to break into the 59-second range per lap on the Tsukuba Circuit, the head mount section cracks due to lack of rigidity around the head. The same is true even with reinforcement, and it is presumed that the frame structure is probably not rigid enough. Also, the engine was also in need of a frame and engine replacement, as the number of over-liter bikes participating in races was increasing and they wanted to use an over-liter engine. The GPZ1100, which had the same engine as the GPZ900R, was chosen.

The GPZ1100 is not for a racing model, but rather a model that has gained a reputation as a touring. Although it is suitable for cruising on a straight line, it is not a machine that competes for time on the track. So, when adopting the GPZ1100 frame, the frame data from the GPZ900R's racer was also used to reconstruct the chassis posture. The caster was raised to improve turning performance, and the pivot position was changed to obtain the proper linkage ratio, among other extensive modifications. Based on the ZRX1200R engine, JE pistons and Yoshimura camshafts were installed. By balancing the weight of internal parts and performing precision assembly, the engine is currently rated at 185㎰ in the winter race. The suspension is a combination of Ohlins inverted front forks and Showa rear shocks. And JB Power Magnesium Forged JB4 wheels are used to improve turning performance. The IMA bracket is currently used to increase the range of settings and to optimize the amount of trail due to the raised caster. The clip-on handles are made by Robby Moto Engineering, and the racer's wishes are also strongly reflected in the unique characteristics of this model.

Engine

ZRX1200R’s engine was selected for base.

Handle

POWER BUILDER's motorcycles are using stock handlebars of other motorcycles, but this GPZ1100 uses Robby Moto Engineering's. The brake master is a radial type made by Brembo. The shape of the levers was modified for optimum touch. This is one of the points that show the attention to detail of the racer.

Chassis

The bracket is a adjustable offset type made by IMA. Initially, it was for GSX-R1000, but due to the caster change, they chose this for the proper offset. The front fork is an Ohlins inverted type, and the internals were replaced with an uprated kit for high-level braking.

The pivot was also changed, as the pivot position was not appropriate for the caster to be set up for turning performance. A vast amount of data from POWER BUILDER was also used to obtain the proper lever ratio for the rear shock.

Brembo radial 4-pot calipers, Sunstar Φ320mm works expanded rotors, JB Power Magnesium Forged JB4, and other first-class parts were used for chassis. By making full use of these parts, The chassis that can withstand high-level riding has been constructed.

Rear shocks were chosen by Showa to match the racer's preference. The shocks are highly reliable enough to complete a lap of the Tsukuba Circuit in less than one minute.

Stock ZZR1200 swingarm was chosen, since it was lightweight and the caster angle and pivot position were determined to be appropriate for the motorcycle posture when those were changed. However, it was not rigid enough, so a stabilizer was added for reinforcement. With this current specifications, even at 185㎰, power is reliably transmitted to the road surface without any problems.

Bodyworks

A smartphone was installed under the meter like a touring user, but this is an Android device diverted for displaying data logger. All of the racer's riding data is recorded in this way, and can be compared with past data. The Stack made tachometer and P-lap device seen in the back of the motorcycle have been removed, and only the Android terminal sits on the meter section. The tachometer can also be displayed on the terminal while riding.

The exterior of the GPZ900R is as itself, but from the seat cowl to the gasoline tank, is an original Power Builder design integrated race tank. The inner tank is also made as a one-off.

Electrical

The data logger was made by Drogger, and sensors were placed at the rear end of the seat rail to research the movement of the motorcycle body. The electrical components were also changed for convenience, such as placing them under the seat and the AS Uotani SPI ignition coils inside the side cowl.

Intake & Exhaust

The exhaust system is special order made by Nojima Engineering for POWER BUILDER. The unique spiral collector is highly trusted by POWER BUILDER for its effectiveness in all aspects, including acceleration, deceleration, and RPM extension.

Gallery

Specifications

About POWER BUILDER

"POWER BUILDER" is a winning tuner in the Taste of Tsukuba, Japan's premier Sunday race for steel-frame bikes from the 80s and 90s. "Power Builder" is a tuner who always wins the Taste of Tsukuba, the most prestigious Sunday race in Japan, where the best bikes from the 80s and 90s compete. Power Builder" is not a restoration company, but rather a company that creates power, a company that is thoroughly committed to creating products that live up to its name.

POWER BUILDER brand page