The TM125 inherits the basic design of the RA factory machine that was very successful in motocross races in Japan. This model features a black-painted 2-stroke 1-cylinder engine mounted on a cradle pipe frame. The engine incorporates an aluminum cylinder with excellent heat dissipation and the Pointless Electronic Ignition (PEI) system. It generates maximum horsepower of 22 PS and is paired with a 5-speed manual transmission that has a close ratio. Other notable features include a slimline fuel tank that can be easily held between the knees, an RH type seat, and a Ceriani type front suspension.

Similarly to the RM250, the RM125 features an aluminum 1-cylinder engine with a 6-port scavenging system that combines a power reed valve and the Pointless Electronic Ignition (PEI) system. This engine is paired with a newly designed semi-double cradle type pipe frame and a 6-speed transmission for smooth acceleration. Other features include the proven rack and pinion clutch release mechanism from the RH factory machine, a Ceriani type front suspension, and a rear suspension with shock absorbers attached at an angle to the center of the frame. The RM125 also features large tires for superior riding performance mounted on light and robust aluminum rims.

This RM125 is equipped with a longer stroke engine with bore × stroke dimensions that were adjusted from 56 × 50 mm in the previous model to 54 × 54 mm. This power reed valve type engine features a 6-port exhaust cylinder head and combines both a rotary valve and power reed valve, which increases maximum horsepower from 25 to 26.5 PS.

The RM125 is equipped with a liquid-cooled engine developed through direct feedback from technologies adopted on factory motocrossers. This is Suzuki’s first liquid-cooled engine for a motocross model. A power reed valve was adopted for the intake system to deliver stable torque from low- to high-rpm ranges. It also features the Full Floater suspension that was introduced to Suzuki’s championship-winning factory motocross racers in the second half of the previous season, and helps to realize superb road holding performance.

This model adopts a new crankcase reed valve type engine, a technology that was directly passed down from factory motocrossers. This valve realizes high filling efficiency across a wide range of engine speeds, improved cooling and lubrication of engine parts, and substantially higher reliability. In addition, the bore × stroke dimensions were changed from 54 × 54 mm to 54 × 54.5 mm. Maximum horsepower was increased from 35.5 to 36 PS.

The competitiveness of the crankcase reed valve type engine was enhanced even further by measures such as increasing the primary compression ratio, widening the main and third exhaust ports, and changing the exhaust valves, resulting in substantially higher power characteristics. The semi-double cradle frame, which incorporates a high proportion of large-diameter angular-cross-section chromium molybdenum steel tubes, was newly designed with the same structure as the RM250 at the rear, further enhancing the balance between lightness, strength, and rigidity.

With this model change, the RM125 features new ellipsoid Automatic Exhaust Timing Control (AETC) valves, which deliver even easier-to-handle power characteristics in the low rpm range. Modified port timing also enhances torque characteristics at low to middle revs. The newly designed frame features an advanced semi-double cradle structure with a better rigidity balance due to the adoption of a rounded pipe for the main tube. In addition, the use of a detachable aluminum subframe enhances the ease of maintenance and reduces the weight around the rear of the bike. Maintenance was also made substantially easier by the adoption of newly developed upright twin-chamber cartridge front forks and a completely redesigned new link-type rear suspension.

Installing the water pump inside the crankcase streamlines the area around the engine, reducing the amount of mud that sticks to the bike during riding, and making it easier to maintain. The shape and timing of the ports, the expansion chamber, and exhaust valves were all re-designed to reflect the latest technological advances, increasing power and torque at all rpm ranges. The rear suspension features an updated link structure and brand new swingarm that create more progressive characteristics, helping to improve shock absorption and road handling even on rough terrain.

Similar to the RM250, the engine and chassis of the RM125 were almost completely redesigned to realize a sweeping reduction in weight, higher power, and greater torque. The result is a bike that creates a superb balance between road handling and controllability. The newly designed engine features a straight intake passage, modified scavenging port timing, and new exhaust pipe dimensions, which help to generate higher power in the mid- to high-rpm range. The weight of the engine was also reduced by 750 g, and its length shortened by 21 mm. While retaining the semi-double cradle frame of the previous model, the specifications and design, including the rigidity balance, weight distribution, swingarm, suspensions, and geometry, were all completely updated. The result is an ideal motocrosser that creates a winning balance with its new high-performance engine.

This full model change of the RM125 pairs a completely new exhaust valve drive system with a triple exhaust port layout that includes a sub-port in place of the dual split exhaust ports of the previous model. This combination enhances engine response at low speeds, as well as traction at medium and high speeds.