The Suzuki RM125-X was their pinnacle bike: lightweight, fast, and equipped with the Full Floater suspension that could absorb anything from small chatter to major whoops with ease. Detractors of this model criticised its difficult airbox (allowing 40 minutes for assembly), fragile clutch, quick-wearing brakes and piston that frequently produced hot spots as source of frustration.
The RM125’s Limits
The Suzuki RM125 features their first liquid-cooled engine, an innovative power reed system to enhance torque characteristics in the low and midrange, and a Full Floater rear suspension specifically tailored for race conditions. The engine itself was developed through direct feedback gathered from technologies adopted on Suzuki factory motocross bikes in 1992, thus making this bike truly remarkable.
This bike quickly spools up with an effortless powerband that delivers serious midrange and top end power. The strong over-rev is also invaluable when jumping, helping this little bike easily get over obstacles with no problem at all.
The chassis of this year’s model represents another key upgrade over its predecessor, boasting an advanced semi-double cradle pipe frame with detachable aluminumaluminiume for easier maintenance and front Showa forks that are 150% superior to those found on 1998 RM125s; they offer sufficient damping and springing pressures that meet most riders in its target demo.
The RM125’s Performance
DirtBike magazine measured it at 32.5 horsepower), but the stock RM125 is fun to ride and more powerful than many bikes of this size. The chassis remains as it was, giving an incredible, feathery ride perfect for tight tracks or sharp corners.
Suzuki implemented changes for 1999 that include lighter front downtubes and changing their frame layout to better centralise mass. They also reduced wheelbase by 5mm for quicker steering response.
The Suzuki RM125’s engine draws heavily on that of a 1998 Kawasaki KX250, but with modified port timing to enhance power characteristics at lower revs. Suzuki utilised bigger carbs than Yamaha or KTM used (standard on 250s). Due to its stiff suspension and abrupt power curve, however, short shifting is essential when riding this bike.
The RM125’s Maintenance
Suzuki engineers made every effort to make the RM125 easy to maintain. By moving the front downtube down towards the bottom of its frame and using thinner rectangular-section material for its construction, mass was centralised while weight was decreased through aluminium components like engine covers, seat rails and footpegs, saving Suzuki money while making life simpler for their riders.
Suzuki made significant modifications to their 1999 engine design, taking inspiration from factory motocross racers. One such technology, a power reed valve, ensures air and fuel can pass freely between piston and crankcase when engine is cold; thus minimising seizing problems associated with earlier water-cooled RM125 engines.
Other improvements included installing a larger 6-blade impeller on the water pump, digital ignition system and wider clutch cable to reduce friction. To enhance suspension performance, they modified fork spring rates as well as added separate triangle-type prop stands that provided more ground clearance while being lighter than frame-mounted stands.
The RM125’s Comfort
Although the RM125 was an ideal bike for novice riders, its top-end power could sometimes be disappointingly lacking for more experienced riders who required something with more top-end punch. Suzuki’s case-reed motor possessed outstanding low and midrange power; however, its top-end power lagged behind other Honda models. To address this in 1992, several updates were implemented that broadened the engine’s powerband: new cylinder scavenging ports increased flow the domed piston helped smooth power delivery, a fuel pump injector improved carb flow while the power valve cover increased exhaust resonance volume by improving flow to the carb.
These changes made the RM125 an ideal choice for expert riders, though it still lagged behind Honda in straight line speed. Suzuki made improvements to suspension as well, but their magic carpet Kayaba forks on Hondas were far plusher in comparison.
For more information on how advancements in suspension technology have influenced motocross, look at our in-depth article “How Video Gaming Became a Global Phenomenon” to see how similar technological advances are impacting trends in sports and entertainment worldwide.