Five-Cylinder Smoker: 1972 Kawasaki S2 415

Up for Auction: 1972 Kawasaki S2 415 with Allen Millyard Engine…  

Allen Millyard has a gift for making the impossible look factory. That has always been part of his magic. Many builders can build a motorcycle that looks outrageous. Far fewer can create something mechanically improbable — a five-cylinder Kawasaki two-stroke, a V12 Zed, a Viper V10 motorcycle — and make it look as though some secret department inside the original factory might have produced it after hours. This 1972 Kawasaki S2 415 is very much in that tradition.

At first glance, it looks like a beautifully restored early Kawasaki triple: slim, bright, period-correct, and unmistakably 1970s. Look a little closer, however, and the illusion begins to shift. There’s too much engine! Too many cylinders, too many exhaust headers. What first appears to be a tidy S2 is actually a rare five-cylinder 415cc Kawasaki special with an engine built by Allen Millyard. And now it’s going up for auction.

This 1972 Kawasaki S2 415 will be crossing the H&H Classics auction block for its National Motorcycle Museum sale in Solihull, West Midlands, on July 22, 2026. The estimate is £18,000–£22,000, and the bike is supplied with a history file, restoration records, an original owner’s manual, and a current V5C. For Kawasaki triple fans, two-stroke obsessives, or anyone who appreciates Millyard’s work, this is a very special little machine.

The Kawasaki Triple Family

Kawasaki’s two-stroke triples were among the defining performance motorcycles of the late 1960s and early 1970s. The 500cc H1 Mach III arrived first and quickly earned a reputation for savage acceleration, light weight, smoky drama, and a certain amount of bad behavior. The 750cc H2 Mach IV took the concept further still, becoming one of the great legends of the two-stroke era.

But the smaller triples had their own charm. The S-series machines brought the same basic formula to more approachable displacements. The 250cc S1, 350cc S2, and later 400cc S3 offered that addictive Kawasaki triple personality in smaller, lighter packages. They had air-cooled, piston-port, two-stroke engines, separate oil injection, three carburetors, five-speed gearboxes, and the kind of hard-edged exhaust note that makes grown adults stop mid-sentence.

The 350cc S2 Mach II was introduced for the 1972 model year and sat in the middle of the range. Kawasaki claimed around 45 horsepower from the 346cc triple, which made it a lively machine in period. It was not as notorious as the 500 or 750, but it carried the same DNA: light weight, a narrow chassis, and a willingness to come alive when the revs rose. For most people, a standard S2 would be interesting enough. Allen Millyard, of course, is not “most people.”

Allen Millyard and the Factory-That-Never-Was

Millyard’s Kawasaki specials have become some of the most beloved custom motorcycles in the world because they are not merely custom in the decorative sense. They are engineering thought experiments made real. Take a production Kawasaki triple, ask what the factory might have built if it had ignored budgets, tooling, and marketing departments, then start cutting, machining, welding, filing, and blending until the impossible looks inevitable.

That approach has produced an extraordinary family of multi-cylinder Kawasaki two-strokes over the years. Millyard has built four-, five-, and six-cylinder variations based on Kawasaki’s original triple engines, ranging from small-capacity specials to massive H1 and H2-based screamers. What unites them is not just the extra cylinders, but the way they look finished.

Millyard’s two-stroke specials have the visual language of production motorcycles: factory-style cases, clean packaging, balanced exhausts, stock-looking chassis lines, and details that appear almost too natural until you realize the original factory never made anything like them. This S2 415 belongs squarely to that lineage.

The 415cc Five-Cylinder

The heart of the bike is a rare 415cc five-cylinder Kawasaki two-stroke engine built by Allen Millyard. Millyard’s first 415cc five-cylinder Kawasaki broke cover at the Stafford Show in October 1996, where it was awarded “Machine of Most Technical Interest.” The concept used five cylinders from an original 250cc Kawasaki triple, creating a five-cylinder engine that retained the spirit of the smaller S-series machines while adding a level of mechanical theater Kawasaki never offered in the showroom. Because the donor 250 triple works out at roughly 83cc per cylinder, five cylinders produce approximately 415cc — hence the S2 415 name.

H&H says it is thought that only six of these 415cc engines were built, with most believed to reside in museums in Japan and the United States. That makes this not just another Millyard-style special, but one of a very small group of engines from a particular chapter in his Kawasaki work.

As with so much of Millyard’s engineering, the idea is simple to describe and fiendishly difficult to execute. Two-stroke triples are compact, but adding cylinders is not a matter of simply bolting extra barrels to the side. The crankcases, crankshafts, ignition, induction, exhaust, and internal oiling all have to be made to work as a unified engine. It must not only run, but run smoothly enough to be ridden…and it does.

A Long-Sleeping Engine, Finished in 2020

The engine in this example was built many years ago, dry-stored for 20 years, and fitted into a period 1972 S2 chassis in 2020. That gives the bike an interesting split history. The engine itself belongs to an earlier phase of Millyard’s work, while the completed motorcycle is a more recent build around that rare powerplant. Last year, the Classic Competition Company gave the bike away via a raffle, and now it’s going up for sale.

The rolling chassis was restored to original specification, and the finished machine is presented in show condition. The seller reports that the bike runs well and is surprisingly economical. 

“This bike pulls so strongly and is happy sat at 70mph or bumbling at 30 if feels very smooth and four stroke like.”

 

There are plenty of cool classic motorcycles, but few make people crouch down, count cylinders, frown, smile, and start asking questions. That is why Millyard’s work resonates so strongly. His machines do not feel like vandalism of the original; they feel like alternate-history extensions of it.

Wait a minute, did Kawasaki actually make that? The answer, of course, is no. Allen Millyard did.

The Auction

As stated above, this 1972 Kawasaki S2 415 will be crossing the auction block at the National Motorcycle Museum in Solihull on July 22, 2026. The estimate is £18,000–£22,000.

Model: 1972 Kawasaki S2 415
Builder / Engine: Allen Millyard-built five-cylinder Kawasaki two-stroke
Registration: EKP 614K
Frame No: S2F 27276
MOT: Exempt
Displacement: 415cc
Engine Layout: Five-cylinder two-stroke, using cylinders from Kawasaki’s 250cc triple family
Chassis: Period 1972 Kawasaki S2 chassis
Exhaust: Handmade stainless 5-into-2 system
Condition: Restored and presented in show condition
Documents: History file, restoration history, original owner’s manual, current V5C
Auction House: H&H Classics
Sale: National Motorcycle Museum, Solihull
Auction Date: July 22, 2026
Estimate: £18,000–£22,000

Auction Listing

H&H Classics: 1972 Kawasaki S2 415
Auction Photos: Gun Hill Studios / H&H Classics

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