Kawasaki GPZ1100 B1/B2

The Kawasaki GPz1100 B1 and B2 are motorcycles that were manufactured by Kawasaki in 1981 and 1982 respectively. Both models featured a four-cylinder, two-valve air-cooled engine design with a capacity of 1,089 cc producing 108 bhp (81 kW) in the B1 and 109 bhp (81 kW) in the B2.^[1] This engine was an evolution of the powerplant used in the previous Kz1000 series, itself descended from the Z1. In 1983 the GPz1100 was completely revamped in both cosmetic styling, suspension and updated engine. The model number changed to ZX1100A1.

Model differences

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, 750 and 550 models.

Handlebars

The B1 had conventional 7/8" handlebars as found on all earlier Kawasaki "Z" series bikes, the B2 had clip on style handlebars that mounted to the top of the fork tube above the top triple clamp, this style then featured on the later ZX1100A models. This style was to continue to be the norm for most sports bikes, especially the Kawasaki GPZ900R series released in 1984.

Instruments

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. The design change also changed the wiring harness and a number of electrical connectors in the front of the motorcycle changed. The speedometer on the B1 is electronic while the B2 is cable driven. The transducer appears to generate a pulse train that is converted to a voltage to feed the speedo meter.^[2]

Brakes

The front disks of the B1 are 10 mm smaller in diameter and 1 mm thinner than the B2, the front calipers 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 brake disk diameter used on the two models require the mounting points to be different.

Fuel injection system

Both the B1 and B2 featured Fuel Injection. The B1 model featured an EFI (electronic) system that was modelled on the 1980 z1000H and (also used in the 1980 z1000G model). This system was a hybrid car design using an air flap that had many reliability issues causing most owners to end up removing it and replace it with the 34mm Keihin CV carburettors used on all the later z1000 and z1100 models. The key problem with the EFI on the B1 was the use of an air-flap design rather than a MAP sensor used in modern systems and the early Throttle Position sensor (TPS) design registered only open or closed (idle) throttle positions. Later models (B2 and ZX1100A)featured DFI (digital) which 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 EFI system was referred to as port injection), while the B2/A (DFI) 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 intake rubbers on the B1 are smaller than the B2 so a throttle body swap is not possible without replacing the inlet rubbers. They are also mounted at a 45 degree angle as the port injector openings are in the way.

Fuel system

The fuel level sender units are physically 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.

Body parts

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. The B1 was only released in 1981 and the B2 in 1982, after that, the dual shock 1100 models ended and the monoshock GPz1100(ZX1100-A1) were released.

References

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

External links

• DEAD LINK, Site has moved Classic Japanese Motorcycle Restoration Web Site This content is now on a page at "z900collector.wordpress.com/restoration/the-gpz1100-collection/gpz1100b2-rebuild/"
• Kawasaki Model History