The Grinch: Kawasaki KX125 Flat Tracker

The Grinch: Kawasaki KX125 Flat Tracker

19-y.o. motorcycle mechanic builds himself a two-stroke tracker… 

The Kawasaki KX125 was the company’s 125cc motocross machine, a lightweight two-stroke weapon that competed for years against the likes of the Honda CR125, Suzuki RM125, and Yamaha YZ125 on MX tracks around the world. Launched in 1974, it would evolve heavily over the three decades, going from air- to liquid-cooled, from twin-shock rear suspension to Kawasaki’s “Uni-Trak” mono-shock system, and much more. It was a bike long-hailed as “easy-to-ride fast.”

For 1993, Kawasaki worked to lighten the KX, giving it an entirely new frame and a slew of weight-saving improvements that shaved about four pounds off the bike’s dry weight — not insignificant in this highly competitive 125 class. They also worked to get more midrange and top end out of the engine:

“On the track in ’93, the KX125 turned out to have one of the best powerbands in the class. The engine ran a lot snappier than in ’92…” –Tony Blazier, The Motocross Vault

While the CR125 was head and shoulder above the rest of the class in top end power, it was a much harder bike to ride, says Blazier.

“Bikes like the KX and RM that year were a lot easier to keep in the sweet spot.”

Enter our new friend Natthan Chasseray (@5temps), a 19-year-old motorcycle mechanic whose spannering career began at an incredibly early age:

“I started mechanics at 7 years old on a 1967 Moto Guzzi Dingo GT50.”

Today he works at Maurice Garage, a vintage motorcycle workshop in Colombes, in the northwestern suburbs of Paris. He’d been wanting to ride flat track for several years, so he picked up a 1994 KX125 to transform into a tracker:

“I built this bike to do flat track, and I wanted to keep the curves of the 80s Kawasaki sportbikes (500/750 h1/h2), with paint that pops in the sun, while having a modern and sporty touch.”

Natthan carried out most of the work himself, cutting and reworking the subframe to fit the tank and fiberglass tail, fitting a set of Yamaha WR250F forks, a newer 2006 KX swingarm, and 19-inch wheels — de rigueur for flat track. The suspension was tuned precisely for his weight and riding style, and he also overhauled the engine, taking peak horsepower from 24 to 35 hp.

He’s nicknamed this two-stroke tracker “The Grinch,” and she’s a hoot to ride:

“It is very light and very handy, but when the exhaust valve opens the beast is released, and the bike only asks to go up to the switch at 15000 rpm.”

Below, we talk to Natthan for more details on the build.

Kawasaki KX125 Tracker: Builder Interview

• Please tell us a bit about yourself, your history with motorcycles, and your workshop.
My name is Natthan, I’m 19 — I work at Maurice Garage. I have been passionate about old mechanics since my youngest age, so I started mechanics at 7 years old on a 1967 Moto Guzzi Dingo GT50.

• What’s the make, model, and year of the donor bike?
This is a 125 KX from 1994.

• Why was this bike built?
It’s a personal project because I’ve wanted to do flat track for several years.

• What was the design concept and what influenced the build?
I built this bike to do flat track, and I wanted to keep the curves of the 80s Kawasaki sportbikes (500/750 h1/h2), with paint that pops in the sun, while having a modern and sporty touch.

• What custom work was done to the bike?
All the modifications were made by me except for the paint as well as the saddle, the numbers, and the headlight plate, and some engine parts.

The frame has been cut in half to fit the tank and the shell. A 250 WRF fork has been adapted as well as a shock absorber and a 2006 KX swingarm.

An engine preparation to go from 24hp to 35hp has been carried out. 19″ rims were also fitted. The suspensions has been prepared to perfectly balance the bike for my weight.

• Does the bike have a nickname?
I called her “The Grinch.”

• Can you tell us what it’s like to ride this bike?
It is very light and very handy, but when the exhaust valve opens the beast is released, and the bike only asks to go up to the switch at 15000 rpm.

• Was there anything done during this build that you are particularly proud of?
I think I’m proud of everything and especially the result.