Kawasaki KH125: A Timeless Two-Stroke Legend

The Enduring Appeal of the Kawasaki KH125

The Kawasaki KH125, a stalwart of the two-stroke era, continues to capture the hearts of enthusiasts with its distinctive character and surprising versatility. Often remembered as a reliable commuter, this diminutive machine also possessed a hidden talent for spirited riding, particularly when kitted out for the track. Its production run, spanning over two decades, is a testament to its enduring popularity and robust design. This article delves into the history, specifications, and practical considerations for anyone looking to experience or restore these classic Japanese motorcycles.

A Glimpse into its Heritage

The KH125, first introduced to the market, quickly established itself as a budget-friendly and dependable mode of transport. However, its potential extended beyond mere utility. With a few modifications, the KH125 could transform into a capable little road racer, a dual personality that endeared it to a broad spectrum of riders. The distinctive styling, with its slender green bodywork and the iconic pink-to-purple gradient Kawasaki logo on the tank, harks back to the vibrant aesthetics of the late 70s and 80s. The high-mounted exhaust, a hallmark of many two-stroke racers, further accentuates its sporting pedigree.

Performance and Specifications

At the heart of the KH125 lies a compact 123cc single-cylinder, two-stroke engine. In its stock configuration, this powerplant delivered a respectable 12 horsepower and 65 ft/lbs of torque. This was enough to propel the lightweight machine, which tipped the scales at a mere 210.5 lbs, to a top speed of approximately 65 mph, with a respectable quarter-mile time of around 19 seconds. The engine was mated to a smooth-shifting five-speed transmission and housed within a sturdy steel-cradle frame. While precise figures for race-spec models are scarce, it's reasonable to assume that modifications would have yielded noticeable improvements in performance.

Key Specifications at a Glance:

The KH100 Companion

It's worth noting that the KH125 was not alone in Kawasaki's 125cc two-stroke lineup. A smaller sibling, the KH100, also graced the market. The KH100 debuted in 1976, the year after the KH125, and shared a production run with its larger counterpart until 1990. While less powerful, the KH100 offered a similar charming two-stroke experience, often appealing to riders seeking a more accessible entry into the world of classic motorcycles.

Bringing a KH125 Back to Life: A Practical Guide

Restoring an old two-stroke like the KH125 can be a rewarding experience, but it requires careful attention to detail, especially for machines that have been dormant for extended periods. A common scenario, as highlighted in forum discussions, involves a motorcycle that has been laid up for many years, often with fuel and old oil still in the system. This can lead to issues like fuel tank rust and gummed-up carburettors.

Key Considerations for Starting an Old Two-Stroke:

• Fuel System: The fuel tank is a prime candidate for rust after prolonged storage. Cleaning it thoroughly, often with solutions like vinegar or specialized tank cleaning kits, is essential. The carburettor will almost certainly require a full strip-down and cleaning to remove any sediment or dried fuel residue. Replacing the float bowl gasket is often a necessity due to age and perishing.
• Lubrication System: This is a critical aspect of two-stroke engines. The KH125, like many of its contemporaries, features an autolube system. However, after long periods of disuse, the oil pump and lines can become clogged or the seals can perish. For initial startup, many enthusiasts recommend using a premix of two-stroke oil and fuel (typically around 20:1 to 40:1 for initial runs) to ensure adequate lubrication for the crank, piston, and small-end bearing. This bypasses the autolube system, providing a more controlled and reliable oil supply until the original system can be verified or rebuilt.
• Engine Internals: Before attempting to start, it's advisable to inspect the engine for any signs of seizure. Gently turning the engine over by hand using the kickstarter is a good initial check. Pouring a small amount of 2-stroke oil directly into the spark plug hole and slowly turning the engine over can help lubricate the cylinder walls and piston rings, especially if the engine has been sitting for a very long time. Listen carefully for any unusual noises, such as grinding or crunching, which could indicate bearing damage.
• Ignition System: Ensure a good spark is present. This involves checking the spark plug, points (if applicable), condenser, and coil. Points can become corroded and may need cleaning with fine sandpaper or contact cleaner. A new spark plug is always a wise investment.
• Gearbox Oil: Don't forget the gearbox! Ensure it is drained of old oil and refilled with fresh, appropriate gearbox oil. A drop in gearbox oil level can be an indicator of worn crank seals.

The Premix Debate: Autolube vs. Premix

The question of whether to use the autolube system or premix is a recurring theme among two-stroke owners. While the autolube system offers convenience by automatically mixing oil with fuel, its reliability in older, unrestored engines can be suspect. Seals can dry out, the pump can seize, or the metering mechanism can fail, leading to catastrophic engine failure. Premixing, on the other hand, provides a direct and visible method of ensuring lubrication. While some debate the precise impact of premix on the fuel-air mixture, particularly with modern ethanol-laced fuels, the consensus for initial startups and for riders with reservations about their autolube system is to err on the side of caution and use premix.

Important Note: When using premix, it's crucial to ensure the autolube oil pump is either disabled or its feed lines are disconnected to prevent the two oil sources from interfering with each other. If you intend to use the autolube system, it's recommended to bleed the pump thoroughly to ensure oil is flowing correctly before attempting to start the engine.

Common Issues and Troubleshooting

Reviving a classic motorcycle often involves tackling common age-related problems:

• Seized Kickstart/Gears: Often caused by old lubricant or debris.
• Perished Rubber Components: Fuel lines, intake manifolds, and airbox hoses are prone to cracking and becoming brittle.
• Corroded Electrical Contacts: Leading to poor ignition or lighting performance.
• Worn Crank Seals: Resulting in air leaks, poor running, and potentially the gearbox oil being drawn into the crankcase (causing excessive smoke).

The KH125's Production End

The Kawasaki KH125 ceased production in 1998. After a commendable and lengthy production run, the model was eventually retired, marking the end of an era for this particular two-stroke offering from Kawasaki.

Finding a KH125 Today

Occasionally, examples of the KH125 surface for sale, often described as 'time capsules' due to their original, unrestored condition. These machines can represent a fantastic opportunity for collectors and enthusiasts. A well-preserved 1979 Kawasaki KH125 Road Racer, for instance, was listed for sale at $6,500, highlighting the value placed on these characterful bikes. When searching for a KH125, look for models that have been reasonably well-maintained, and be prepared for the potential need for recommissioning, especially if the bike has been stored for a significant period. The availability of spare parts, while not as ubiquitous as for some more modern machines, is generally manageable within the classic motorcycle community.

Conclusion

The Kawasaki KH125 stands as a charming example of Japanese two-stroke engineering from a bygone era. Its blend of commuter practicality and sporting potential, coupled with its distinctive styling, ensures its continued appeal. Whether you're a seasoned restorer or a newcomer to the world of two-strokes, the KH125 offers a rewarding ownership experience, embodying the simple joys of riding a well-crafted, characterful motorcycle.

Frequently Asked Questions

When was the Kawasaki KH125 discontinued?

The Kawasaki KH125 was discontinued in 1998.

Should I use premix in a KH125?

For initial startups and if you are unsure about the condition of the autolube system, using a premix of 2-stroke oil and fuel is highly recommended to ensure adequate lubrication.

What are the typical performance figures for a KH125?

A stock KH125 produced around 12 horsepower and could reach speeds of about 65 mph.

Is the KH125 a good beginner bike for two-strokes?

Yes, the KH125 is often considered a good entry-level two-stroke due to its relatively simple design and forgiving nature.

Where can I find a workshop manual for the KH125?

Workshop manuals can sometimes be found on eBay or through specialist classic motorcycle parts suppliers. Online forums dedicated to Kawasaki motorcycles may also have resources or links.

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