Kawasaki GPZ1100 B1/B2

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In 1981, Kawasaki released the GPz1100B1 followed by the GPz1100B2 in 1982. Both models featured a 4 cylinder, 2 valve air-cooled engine design with a capacity of 1089cc. The design was similar to previous engines used on the popular z1000 series, in particular the z1000-A4 MkII engine design. In 1983 the GPz1100 was completely revamped in both cosmetic styling, suspension and engine design. The model number changed to zx1100A1 and the engine featured a four valve design.

Cosmetically, both the B1 and B2 were released in a bright red paint called "Firecracker Red", the B2 was also available in a gold colour called "Sonic Gold". The red colour theme was a departure from early colour schemes and started the marketing campaign called the "Red Revolution" featuring the 1100, 900 and 750 models.

The B1 had conventional handle bars as found on all earlier Kawasaki "Z" series bikes, the B2 had bars that resembled clip on handlebars, but mounted on top of the forks, this style was to continue to be the norm for most sports bikes, especially the Kawasaki GPZ900R series released in 1984. As a result of the handle bar mounting, the top triple clamp is different between the two models.

The Instruments on the B1 used bulbs for all warning lights and featured a Speedometer, Tachometer, Fuel Gauge and Voltage Meter. The B2 instrument panel feature the Speedometer and Tachometer but the fuel gauge and most of the warning indicators were replaced with an LCD assembly. The design change also changed the wiring harness and a number of electrical connectors in the front of the motorcycle changed,

The front disks of the B1 are 10 mm smaller in diameter and 1 mm thinner than the B2, the front callipers are also different but the disk brake pads are the same. The rear disks are identical in both models.

The front forks are slightly different between the two models. Both models feature air assistance, but the B1 model uses an air valve located at the top of the fork leg while the B2 uses an equaliser tube linking the two tube with a single air valve. By using an equaliser tube, each inner fork tube requires a small hole to allow the air in. The lower legs are different as the different callipers used on the two models require the mounting points to be different.

Both the B1 and B2 featured Digital Fuel Injection (DFI). The B1 model featured a DFI system that was modelled on the 1980 z1000H and (also used in the 1980 z1000G model) This version of the DFI system was a hybrid car design that had many reliability issues causing most owners to end up removing it and replace it with z1000J carburettors. The key problem was the use of an air-flap design rather than a MAP sensor used in modern systems and the Early TPS design registered only open or closed (idle) throttle positions. Later models (B2 onwards) used a variable TPS that accurately represented the throttle position and hence a better Electronic Control Unit (ECU) algorithm called "Alpha-N".

On the B1 model, the four fuel injectors are mounted directly into the cylinder head above the inlet ports (hence the DFI/EFI system was referred to as port injection), while the B2 model had the more common Throttle body injection (TBI) where the injectors are mounted into the throttle bodies. With different throttle bodies comes a very slight difference in the air box mounting.

The fuel level sender units are different between the two models, this could be due to the different methods used to report the fuel level (B1–gauge, B2–LCD). The B1 model has a fuel sender with a round tank mounting, the B2 has a rectangular mounting plate, therefore the tanks are different also. The DFI fuel delivery hardware appears to be the same. The 1983 model also uses the same fuel pump and TBI setup as the B2.

The B2 model featured a Bikini fairing, this resulted in a change in a number of cosmetic covers and the addition of extra mounting brackets. Because of the bikini fairing, the headlight assembly is slightly different between the two models. The frames are basically the same with a few subtle differences in the fasteners used.

The tail light of the B2 features a reflector on each side of the rear lens. The internals of the lens are also different between the two models. The tail light lens feature identical mounting, so they can be interchanged.

According to first hand accounts from owners and dealers, the B1 and B2 models had a number of issues that were addressed by Kawasaki in and out of warranty periods.

• Front Disk warp on B1 models, rectified by Kawasaki in the B2 with larger (and thicker) disks.
• Injector failure on B1 models, Port injection replaced with TBI in B2 model.
• EFI failures (numerous) The common failure observed by many was theThrottle position sensor (TPS) electrical connector failing. This fault typically occurred several years out of warranty. For most owners common solution was to replace the TBI with carburettors!
• Engine paint flaking in both models, paint evolution continued into GPz900R range, no real cure applied.
• Side stand mounting point breakage.
• Seizing disk brake calliper piston.
• Rear disk cracking.
• Seizing bottom headstock bearing (lack of grease).
• Uneven disk pad wear.
• Rear shock absorber failure.
• Poor finish on black chrome exhaust system.
• Cracking plastic switchgear in B1 model. New design in B2 models onwards.
• Fork oil seals failing and leaking oil.
• Excessive oil consumption. The piston sleeves were bored external to the barrels and then distorted when in use. Solution was to rebore the barrels.
• Twisted crankshaft caused by missed gears at high RPM causing alternator flywheel to over spin.

The main failure of the B1 and B2 models and subsequent models was Kawasaki's EFI/DFI system. The failure of any component in the system caused reliability issues which caused owners to change over to trusted technology.

This article includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations. Please help improve this article by introducing more precise citations. (July 2008) (Learn how and when to remove this message)

• Kawasaki Motorcycle Parts Catalog - Z1100B(GP) For Export Market December 11 1981

• Classic Japanese Motorcycle Restoration Web Site
• Kawasaki Model History
• GPz1100 Model History from z-power
• How Fuel Injection Systems Work