Kawasaki KMX125 Buyer’s Guide: A Green-Laned Icon Worth Owning?
Few learner-legal motorcycles capture the spirit of the late 1980s quite like the Kawasaki KMX125. First registered for UK roads in 1987, the KMX arrived at a time when the 125cc learner laws had firmly reshaped the market, pushing manufacturers to extract maximum excitement from small-capacity machines.
Japan responded with a new generation of trail-styled learner bikes that looked like full-blown off-roaders but complied with UK regulations. Kawasaki’s answer was the KMX125 — a liquid-cooled, two-stroke single with bold motocross-inspired styling, acres of plastic, flexible indicators, handguards and a purposeful stance that made it stand out on the school bike racks of the era.
Engine and performance
At the heart of the KMX125 is a 124cc liquid-cooled two-stroke engine featuring KIPS (Kawasaki Integrated Power Valve System). This system varied exhaust port height and used a resonance chamber to improve low-rpm torque while maintaining strong top-end power. In UK-restricted form, output was limited to 12bhp, but unrestricted versions were claimed at 22bhp, with period tuning mods reputed to push figures much higher.
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Even in standard trim, the KMX was lively and engaging, offering strong mid-range punch and easy rideability. Its light weight and agile handling made it particularly appealing for green-laning and trail riding.
How it compared to rivals
The KMX125 competed directly with machines such as Yamaha’s DT125LC, Honda’s MTX125 and Suzuki’s TS125X. While the Yamaha was often regarded as slightly faster and sharper-handling, the Kawasaki earned a reputation for being robust, well built and capable of standing up to hard use. In truth, brand loyalty, dealer access and availability often decided which bike riders chose.
What to check before buying
As with any 1980s trail bike, condition is everything. Most KMX125s led hard lives and few escaped being dropped at least once.
Key areas to inspect include:
- Engine: Pistons and rings are service items. Expect worn main bearings on higher-mileage bikes and possible crank rebuilds. Crank seals can leak.
- KIPS valve: Requires correct servicing and setup — neglect can affect performance.
- Suspension and running gear: Bearings, linkages, forks and brakes often need overhaul. Fork pitting is expensive to fix.
- Tank: Prone to rust and paint bubbling. Fuel stains may indicate serious corrosion or failed liners.
- Plastics: Crash damage and ageing are common; original panels are increasingly hard to source.
- Exhaust: Front pipes are frequently damaged. Look for welded-in restrictor washers from the learner-legal period.
- Electrics: Simple systems but now ageing; side-stand switches can cause problems.
- Cooling system: Bikes run on tap water may suffer corrosion or leaks.
What to buy and how much to pay
Buy the most complete, original example you can find. Restoring a rough or incomplete bike can quickly become uneconomical due to the scarcity of good plastics and tanks.
Prices remain relatively sensible. At the time of writing:
- A 2002 example with 21,000 miles and an MoT was offered at around £870
- Late-1980s and early-1990s bikes were advertised just under £1900
- A tidy auction example recently sold for £1500 plus fees
Occasionally, a KMX125 fitted with a KMX200 engine surfaces — a rare and entertaining upgrade for those lucky enough to find one.
Why the KMX125 still appeals
Four decades on, any learner-legal two-stroke still running is something worth celebrating. The KMX125 remains easy to ride, light, manoeuvrable and surprisingly capable off-road. Its tall seat height quickly disappears once seated, making it accessible even for smaller or older riders.
Slim, characterful and full of period charm, Kawasaki’s KMX125 might just be the trail bike you never knew you needed.
The original article was in Classic Motorcycle Mechanics Magazine. Words by Steve Cooper. To subscribe please visit https://www.classicmagazines.co.uk/classic-motorcycle-mechanics
