Two-Stroke Triple: Kawasaki S2 “V2.0” by Brian Cox

Kawasaki S2 Cafe Racer

In 1972, Kawasaki introduced the S2 Mach II, a 350cc two-stroke triple that made 45 horsepower at 8000 rpm and weighed 330 pounds. Unlike its legendary big sibling, the widow-making 500cc H1 Mach III, the S2 was more than just a straight-line machine:

“The Mach II was an entirely flickable bike, with the narrow engine (two inches less than the 500) giving it great cornering clearance.” —Rider

Unfortunately, the S2 was fated to last just two years — 1972-1974 — making it an exceedingly rare machine today.

Kawasaki S2 Cafe Racer

Enter one of our favorite builders, Brian Cox (@Classicbikebuilding), who’d been squirreling away a ’72 S2 for some years, waiting for the right time to build it. Brian has been infected with the motorcycle bug for nearly 50 years now, ever since his older brother introduced him to the two-wheeled obsession at the tender age of 5. Today, he works out of his single car garage, which he’s equipped with many of the more old-school and time-honored tools of the trade:

“I appreciate the tools’ history because I’m attempting to reverse time with the construction methods I’m using in my builds.”

Kawasaki S2 Cafe Racer

This fall, at the coaxing of a friend, he decided it was time to dig the S2 out of storage and finish the build. He had a vision for a lighter, sleeker two-stroke triple that would resemble the cafe racers of an earlier era. Most of the design work happens in his head:

“I don’t have CAD and I can’t draw, so I imagine it and build wire patterns to get the shape I want before I cut metal.”

Brian has touched nearly every piece of this bike, inside and out. Not only has the engine been rebuilt and the frame cut and rewelded in places, but he’s hand-made and turned every single aluminum bracket, both those you can see and those you can’t.

“It would be easier to tell you what I have not made custom in this bike than what I have.”

Kawasaki S2 Cafe Racer

The aluminum bodywork is simply staggering, made from flat sheets of aluminum that Brian cuts, hammers, English wheels, straightens with hammer and dolly, gas-welds, sands, and polishes.

“I love making the hand-hammered aluminum using old tools and old techniques. That’s what I’m the most proud of on this build.”

Kawasaki S2 Cafe Racer

Recently, the bike was featured in The One Motorcycle Show 2020, where it was a standout among standouts.  Below, we get the full story on the build. Photos from Eddie Del Valle (@bearded_r0b0t) and the Coxes themselves.

Kawasaki S2 Cafe Racer: Builder Interview

Kawasaki S2 Cafe Racer

• Please tell us a bit about yourself, your history with motorcycles, and your workshop.

Hello, my name is Brian Cox. My older brother started me out with motorcycles when I was 5. I was immediately infected with this motorcycle bug and have remained uncured for the past 49 years since. I’ve ridden, raced, repaired, and built motorcycles as much as my schedule and budget would allow. I have somewhere in the neighborhood of 17 motorcycles right now. I’ve built or modified many of those in my single car garage that I use as my workshop. I store my bikes in a shed that I built, so the garage is my dedicated workplace. I’ve managed to equip my shop fairly well; although, mostly with tools like my 1956 Southbend lathe which I acquired at a garage sale. A lot of my metal working tools and many of my shop tools have a history before me with some other mechanic, fabricator, etc. I appreciate the tool’s history because I’m attempting to reverse time with the construction methods I’m using in my builds.

Kawasaki S2 Cafe Racer

 

• What’s the make, model, and year of the bike?

The Kawasaki is a S2 350cc triple two stroke produced in 1972.

• Why was this bike built?

I built this bike because I had it! I squirreled this bike away quite a few years ago because it’s unique. This model was only produced for two years so I’ve wanted to build it for a LONG time. This past November 13th a friend who is also a builder asked me what I’d be taking to the shows this year? I was in the middle of completing the hand-formed aluminum on a customer’s build at that time and told him I had nothing built. He gave me some grief over that, and as I finished that customer’s bike I kept thinking of this bike. So, the second week of December I dug this Kawasaki out of storage. The frame and engine I’d redone earlier, so I had a little head start, but this bike was built because I’d wanted to build a two stroke triple since my childhood. I had this motorcycle partially rebuilt and I thought I could complete it in the time frame of December and January having it ready to show by February.

Kawasaki S2 Cafe Racer

• What was the design concept and what influenced the build?

By modern standards, I’m a horrible design/concept person. I’ve appreciated everything motorcycle since I was 5. With this Kawasaki, I had a 1972 motorcycle with all the square and upright riding position of that era. I wanted to reverse the age a little and make it resemble an earlier era cafe racer while removing weight and making it sleek. The rest of the design was inside of my head. I don’t have CAD and I can’t draw, so I imagine it and build wire patterns to get the shape I want before I cut metal. That’s about the entirety of my design process; it’s what I imagine and that must come from what has influenced me at some point in my life.

Kawasaki S2 Cafe Racer

• What custom work was done to the bike?

I basically make almost EVERYTHING shiny by hand. I’ve cut and re-welded sections of this frame and removed every unnecessary bracket. I started from there. I cut the fender brackets from the front forks and polished the legs on my lathe, I completed every piece of hand-formed and gas-welded aluminum on the body, I moved or removed the conventional oil injection tank, battery box, and air cleaner.

I’ve updated the electronics with Lithium Ion optimized charging, electronic ignition, LED lights, and electronic instrumentation. I’ve handmade and turned every aluminum bracket from the seat frame and oil tank that you can’t see to the handmade rear sets. I built the wheels and the exhaust, and some controls are about all I did not build personally. I even took the original switch controls apart so I could polish the housings, and I make my own cables to the appropriate lengths. It would be easier to tell you what I have not made custom in this bike than what I have. I even completely rebuilt the entire engine; it’s new inside (I’ve not had enough time to get the jetting completely sorted out yet, but it’s close).

Kawasaki S2 Cafe Racer

• Does the bike have a nickname?

I named this one “V2.0,” that stands for Version 2.0 as this is my vision of an updated version of the two stroke from the golden age of the two stroke.

• How would you classify this bike?

I classify it as Cafe Racer (strong emphasis on “race-er”).

• Was there anything done during this build that you are particularly proud of?

All of my aluminum work is handmade using the old-school methods. There’s a lot of small things I did to this bike, but the one thing I’m the most proud of is making the aluminum bodywork from flat sheets of aluminum that I order, cut, hand hammer, English wheel, straightened with a hammer and dolly, and then gas welded together before sanding and polishing it all. I love making the hand-hammered aluminum using old tools and old techniques. That’s what I’m the most proud of on this build.

Kawasaki S2 Cafe Racer

Follow Builder Brian Cox @Classicbikebuilding

 

2 Comments

  1. Bill Dancliff

    This is real craftsmanship by hand not tig and CADD. Few of us can gas weld aluminum.

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