Flat-trackers and two-strokes are some of our favorite things. Combine the two, and we’re hooked.
All the more if the two-stroke in question is the mythical Kawasaki S1—an air-cooled triple celebrated in its heyday for being a spirited ride. This 1975-model S1 belongs to Aaron Pierson, who’s done a stellar job of transforming it into what he calls “The Mach Chicken.”
Aaron hails from Lethbridge in Alberta, Canada, where he builds and tests turboprop engines for an aircraft engine manufacturer. His family used to run a Kawasaki shop, which is where he first came across his S1.
“When I was fourteen, I dug the motor out of a trailer we had at our shop,” he says. “It had originally come from a hill climb bike that we built for a local guy. It was heavily ported, and had S3 carbs on it.”
Aaron stored the engine for many years—until he eventually decided to revive the old ‘Mach 1.’ “I purchased an old, ugly chassis and started building.”
The engine was still in excellent shape, but that didn’t stop Aaron from pulling it apart and giving it a thorough inspection. In the process, he shaved the heads a tad to bump up the compression, and overhauled and rejetted the carbs. He gave the frame a solid once-over too—removing tabs that weren’t needed, and adding new ones in the right places.
He then set about making a new set of expansion chambers for the exhausts, from scratch. “I acquired a set of rolled cones,” he explains, “then bought a TIG welder and taught myself to weld while making the pipes.”
A dig around his father-in-law’s barn yielded a vintage Carlisle rear tire, and a brand new Yamaha TY250 seat. “He bought it new for his hill climbing YZ years ago,” says Aaron, “but he didn’t use it often—so it was in pristine condition.”
Not wanting to wreck a rare find, Aaron only bent the seat brackets slightly to mount it. In front is the stock S1 tank; both have been finished in a crisp, classic Kawasaki paint scheme.
The parts bin additions don’t stop there: Aaron installed 70s Marzocchi shocks from a Hercules GS250, solid aluminum bars from his “parts pile,” and a spare choke lever from a Kawasaki H1R project he’s working on. The clutch lever is from Works Connection, and the foot pegs are from his Husqvarna dirt bike.
The original wheels were stripped, painted and re-laced, with a new Duro tire fitted up front. The stock drum brakes were refurbished and drilled, and the original forks rebuilt and retro-fitted with custom-made preload spacers.
Aaron also tore into the electrics—building a new, simpler wiring harness from scratch. The ignition’s now controlled by a Yamaha WR450 push button, and there’s a modern rectifier and regulator. Under the seat is a small gel battery and there’s a switch on the bars to flip between low, high and strobe for the LED headlight.
The running gear’s been kept simple. There are no mirrors, turn signals or fenders, keeping it “as true to a race bike as possible.” There is a speedo though: the original S1 unit, minus the factory bezel. And Aaron has added an inner fender out back, in the form of an aluminum block-off plate that doubles up as under-seat storage.
“It houses the battery, regulator, battery charge connector, three spare spark plugs, spark plug wrench, Phillips driver and flat head screwdriver. Best of all, it’s accessible with only two spring pins.”
There’s a host of other details that would take us hours to list, but the real question is whether all the effort was worth it.
Apparently, it was: “This bike is a riot to ride! It always turns heads, and I’ve had it sideways as many times as any flat tracker should!”
Photos by Aaron Pierson | Peace And Wheelies