Six-Cylinder Z1 from Allen Millyard…
Lately we’ve been highlighting a few of the mind-blowing shed-built specials from one of the world’s most legendary builders, Allen Millyard. As many of you know, Millyard is a retired nuclear research engineer (aka rocket scientist) who began earning acclaim in the early 2000s for rebuilding 1970s Kawasaki two- and four-stroke engines with more cylinders and different layouts than anyone would think possible…especially for a mild-mannered, tea-drinking English gentleman working in his garden shed.
“He cuts crankcases with his hacksaw, has a great selection of dressing files and heats aluminium cases up in his barbecue so he can weld them. He doesn’t use drawings or CAD for any of his work, he has a 3D mind. If Allen can see it, he can build it.” –The Motorcycle Broker
Apart from larger-than-life specials like his 5000cc V-twin “Flying Millyard” special and Viper V10 bike, Millyard generally goes for a factory look, creating bikes even an enthusiast might mistake for a stock restoration at first glance. Only when you notice the extra cylinders and exhaust pipes does it dawn on you that something strange — and strangely awe-inspiring — is going on here.
Most recently, we featured Millyard’s Kawasaki Z2300 V12 and Z1600 V8, both of which now reside in Alabama’s famed Barber Vintage Motorsports Museum. The latter was based on the mighty Kawasaki Z1, the original 900cc Zed that stole the thunder from Honda’s CB750 and birthed one of the world’s most iconic series of sporting motorcycles.
The Zed remained a dominant force in the superbiking world throughout the 1970s. Toward the end of the decade, however, Honda responded with the CBX1000, a six-cylinder machine meant to be bigger, faster, and more impressive than any superbike before it. While the CBX was more successful in some ways than others, Kawasaki didn’t respond with their own six-cylinder until the KZ1300, which was liquid-cooled and shaft-drive — more Goldwing than UJM superbike.
But what if there had been a six-cylinder air-cooled Kawasaki Zed? Well, Millyard is the man to build an answer to that very question. Over the pandemic lockdown, he built a pair of Kawasaki Z1 “Super Six” specials. Millyard has said he especially likes these builds because the inline layout (as opposed to the V8) means you can’t even tell the bikes are modified from the side. Talk about sleepers!
The first build took him just over three months using a restored Kawasaki Z1 900 along with two Z1 engines. The blue bike you see here is reportedly 1396cc, while the red one is 1522cc due to Millyard using the slightly larger sleeves from a later 1015cc Z1 engine.
Of course, turning a four-cylinder into a six is no walk in the park. Millyard has a full flock of videos, shared below, which document building the Super Six crankcases, crankshafts, cams, heads, exhausts, and more.
Interestingly, the two additional cylinders were actually added to the center of the new engine. Millyard cut the first engine in half, then added cylinders two and three from the second engine. He had to re-engineer the balance weights of the crank, as they were in all the wrong places, and worked out the firing order (1-4-2-6-3-5).
“I use a 120-degree crank so the middle cylinders are offset by 120, then the next two and then the outermost two. So you end up with a standard firing order.” -Millyard, MCN
The resulting engine is impressively narrow considering the extra cylinders — we’re not sure of the actual dimensions, but a CBX certainly looks wider to the eye. Not surprisingly, the engine sounds incredible, as demonstrated in Millyard’s first ride video (more below).
Paul Jayson of The Motorcycle Broker was fortunate enough to test-ride the bike and give the observations of someone less accustomed than Millyard to riding such feats of engineering.
“The joy of a motor that feels like it has more torque than a jumbo jet is truly blissful. As there are so many cylinders firing all at once, it sounds like it’s revving far higher than it really is.”
Below are more of Millyard’s information videos about the build — we highly recommend them. And make sure to check out more Millyard specials below.
Super Six Videos
This is the first video in Millyard’s 19-video playlist dedicated to the Super Six builds. You can hit the emblem in the top right corner to skip ahead to the other videos. Millyard is an absolute treat to watch — enjoy!
https://www.youtube.com/watch?v=videoseries
Follow the Builder
Instagram: @allenmillyard
YouTube: @AllenMillyard
More Millyard Specials
Super Six II: 1522cc Kawasaki Z1 Six-Cylinder – Allen Millyard’s Second, More Powerful Six-Cylinder Zed… In our estimation, Allen Millyard is nothing short of a motorcycling treasure. While the retired nuclear engineer and motorcycle mad scientist hails from England, his creations have dropped […]
World’s Smallest V-Twin Motorcycle: Honda “SS100” – 99cc Honda SS50 V-Twin from Allen Millyard… Introduced in 1967, the Honda SS50 was a schoolboy’s dream. The 49cc OHC four-stroke featured a long race-style tank, gorgeous heat-shielded high-line exhaust, and even a café-style bum […]
Shed Zed: 1396cc Kawasaki Z1 “Super Six” – Six-Cylinder Z1 from Allen Millyard… Lately we’ve been highlighting a few of the mind-blowing shed-built specials from one of the world’s most legendary builders, Allen Millyard. As many of you know, Millyard is a […]
The Z1600: 1600cc Kawasaki V8 Motorcycle – Allen Millyard’s Kawasaki “Z1600” V8 Special… Recently we’ve been doing a number of features on the mind-blowing creations of Allen Millyard. The mild-mannered tea-drinking English gentleman is renowned for constructing bikes around his own shed-built […]
2300cc Zed: Kawasaki Z2300 V12 Motorcycle – 2.3L Kawasaki KZ2300 V12 Special from Allen Millyard… If you love motorcycles and haven’t been living under a rock for the last quarter century, you likely know the name Allen Millyard. The UK-based shed builder […]
1000cc Widowmaker: Kawasaki H2 Mach IV 1000-4 – 120-bhp 1000cc 4-cylinder Widowmaker from Allen Millyard… Introduced in late 1971, the Kawasaki H2 Mach IV 750 was the fastest-accelerating, scariest production machine money could buy. The 748cc air-cooled two-stroke triple-cylinder engine made 74 brake […]
The Millyard Viper: 8000cc Viper V10 Custom Motorcycle – Allen Millyard’s 8000cc, 500-bhp Motorcycle Special… Engineer and custom bike builder Allen Millyard will go down as one of the greatest custom motorcycle builders of the past century, best known for his multi-cylinder specials […]
5000cc V-Twin! “The Flying Millyard” – No Replacement for Displacement… Allen Millyard is nothing short of a living legend, an engineer and custom bike builder best known for his mind-blowing multi-cylinder motorcycle specials that defy mechanical belief. The first time we […]
5-Cylinder Kawasaki 2-Stroke by Allen Millyard – The Kawasaki Triples were some of the most notorious motorcycles ever made, a series of 2-stroke street demons that prompted Hunter S. Thompson to write: I still feel a shudder in my spine every time […]
