Following in the footsteps of Japanese car companies, Earlier this year Kawasaki launched a Heritage Parts program. The first item to be reproduced was the cylinder heads for the 1972-76 Kawasaki 900 Super 4 and the 1973-78 Kawasaki 750RS, also known as the Z1 and Z2, respectively, and considered two of the company’s most iconic bikes. The first run of 1,000 cylinder heads sold out in two hours, but Kawasaki is making more, including 50 limited edition desk art cutaways.
The Z1 sold over 100,000 units worldwide, and was so beloved that Kawasaki even launched a homage bike, the Z900RS, a few years ago. They were popular platforms for modification, and spawned a thriving aftermarket. In fact, it is said in Japan that if you can complete an entire restomod Z1 if you have only the frame and engine.
And therein lies one of the problems — you need an engine. After nearly 50 years, usable motors were beginning to get scarce. Talking to fans and owners, Kawasaki learned of the need for engine parts. Kawasaki realized that cylinder heads were too costly for a small aftermarket company to invest in and that only they, the original manufacturer, had the ability to make them.
So, they began to do research in 2018. According to the Kawasaki team members who worked on the project, they had to modernize production based on paper blueprints and diagrams drawn in 1972. It’s a tale we’ve heard from companies like Honda and Toyota, who each faced similar challenges with their heritage parts programs.
Scanning them was no small task. According to team lead Takafumi Matsumoto, even the handwriting on the old documents was difficult to read. The team had to scan drawings into a computer and convert them from 2D to 3D in order to use the modern equipment that the company owns nowadays. Norikazu Matsumura, project supervisor, said that just removing the graph paper’s grid lines in the scan took three weeks. It took another three weeks to make the characters and lines consistent.
Ryo Iwata, who was in charge of digital modeling, said that when he joined the company 20 years ago he was already drafting with CAD, so he lacked experience modeling from hand-drawn blueprints. He thought that the parts may not fit exactly once translated to 3D, but to his surprise, every side and corner fit exactly. “The designers at that time are amazing!” he thought.
As such, the cylinder heads aren’t exactly the same as the originals, made instead with modern design standards, manufacturing technologies, and methods. For example, rather than replicate the inferior materials of the originals, they’re cast with a modern aluminum alloy. It’s Kawasaki’s own blend, the same one used in the ZX-10R’s engine.
The new heads also have much thinner cooling fins. However, the originals were thicker due to the manufacturing limits at the time, and the thinner fins actually match what was in the original blueprints.
One decision they had to make was to cast holes for M8 studs for the exhaust manifold. Though the majority of the original cylinder heads used M6 studs, the original design was upgraded for 1976 and up models because the thinner studs had proven to be a weak point back in the day. Buyers will have to enlarge the holes in their exhaust manifolds, but it should be a minor concession.
Kawasaki didn’t cut corners, either. The four bearing caps for the camshafts required four different molds because the originals were embossed with the numbers 1 through 4. It would have been far easier to create a single mold for all the bearing caps, especially on a part that few people would ever see, but Kawasaki wanted to stay as true as possible to the original. The end result is a work of art.
These cylinder heads are built at Kawasaki’s Akashi factory and come in two colors, silver and black, costing ¥253,000 ($2,390 USD) and ¥264,000 ($2,490 USD) respectively. The initial run was of 1,000 units, but production’s not limited to that number. As of now, they are only available in Japan but Kawasaki says they are considering overseas sales.
If you don’t need an entire cylinder head, Kawasaki is also offering a cross-section cutaway mounted on a wooden stand. It almost seems like a shame to cut them up, but these pieces of desk art commemorate the launch of Kawasaki’s Heritage Parts program and can be purchased for ¥25,000 ($235 USD). Only 50 will be made, each with a serial numbered plaque, and the privilege of buying one will be determined via a lottery system.
Kawasaki also says they’re considering parts for other models. In particular, they acknowledge they’ve received many requests from owners of the W and Mach series. It’s heartwarming to see more and more Japanese companies taking in interest in making these types of parts, as Mazda is doing for the NA Roadster/Miata, Nissan for the R32, R33 and R34, Honda for the Beat, and Toyota for the 2000GT, A70 and A80 Supra. If you live in Japan, you can get your Kawasaki Heritage Parts here.
Images courtesy of Kawasaki.