Suzuki RM125 Specs and Review

The Suzuki RM125 is preceded by its irrefutable reputation, having dominated the World Motocross GP championship from 1975 to 1984. This famed two-wheeler is light, powerful, and has an interesting history. This article will cover this Enduro-style dirt bike and the groundbreaking innovations it introduced in the motorcycle industry.

Produced from 1974 to 2008, the Suzuki RM125 signaled the beginning of the Japanese firm’s “Racing Model” series. It featured a “Full Floater” suspension system, 6-speed manual gearbox, and up-swept exhaust that enabled it to best its competition and land Dirt Bike Magazine’s “Hall of Fame.”

A replacement to the Suzuki TM125, the RM125 expectedly surpassed the capabilities of its predecessor. However, very few off-roaders know that the 125-cc RM models had a shaky start. Despite this, the launch of the dirt bike was such a massive success that the range quickly stretched out to include 50-cc to 400-cc displacements.

Curious as to what makes the RM125 one of the finest MX bikes ever built? Read on – this guide has got you covered.

Yellow 2003 Suzuki RM125 Dirt Bike

Suzuki RM125 History

Unknown to many, the RM125 did not hit the ground running during its launch. In fact, it was not powerful enough when tested against the likes of Honda CR, Kawasaki KX, and Yamaha YZ models. In a last-ditch effort to change this ‘first impression,’ Suzuki almost hurriedly released the RM125S halfway through the year. The company did so successfully – and yet, the machine was plagued with cold-seizing problems until 1980.

Significant alterations did not happen until the year after when the Japanese firm equipped the dirt bike with liquid cooling and gave it new cylinder linings and several piston design improvements. It was also in 1981 that Suzuki utilized the “Full Floater” suspension system on the two-wheeler. Add in an adjusted saddle, a new power reed system, and a manual gearbox that was 20% stronger, and the RM 125 was officially MX-ready.

All RM125 models continued to receive design and styling enhancements until Suzuki decided to discontinue the 125-cc RM in America due to industry changes in class structure. These enhancements improved the MX bike’s stock attributes and addressed any minor mechanical flaws it had. Suzuki champion racers Gaston Rahier, Akira Watanabe, Harry Everts, Eric Geboers, and Michele Rinaldi could not have been prouder.

Suzuki RM125 Specs & Features

Produced from 1974 to 2008, this dirt bike released a total of 36 models throughout its production run – all 2WD and in Champion Yellow body panels. To be better acquainted with the evolutionary changes the RM125 underwent, let us compare the ’75 and ’06 models in this section:

Engine

The RM125’s power mill was not always mated to its current Mikuni TMX38SS carburetor. Its initial 28-mm carb did not make the Enduro-styled bike powerful enough against its Honda, Kawasaki, and Yamaha counterparts. This realization called for mods halfway through its debut year – which led to increasing the carb size to 34 mm, along with other engine upgrades. But what stood out the most from these changes was not the larger cab or the mods done on the wheeler’s “downpipe” exhaust. It was the use of pink poly hoses for the overflow tubes on the revisited model.

1975 Suzuki RM 125 2006 Suzuki RM 125
Engine Type 2-stroke
Cylinder Arrangement 6-port scavenging, piston valve Crankcase reed valve, single-cylinder
Carburetion System Carburetor, 28-mm Mikuni (RM125M);
Mikuni VM34SS (RM125S)
Carburetor, Mikuni TMX38SS x 1
Engine Cooling Air cooling Liquid cooling
Engine Fuel Unleaded gasoline of at least PON 86/RON 90 rating (RON 95 – non-U.S./Canada), containing < 5% MTBE, < 10% ethanol, or < 5% methanol
Fuel Capacity 5.3 L/1.4 US gal 8 L/2.1 US gal
Bore x Stroke Ratio 56×50 mm (2.20×1.97 in) 54×54.5 mm (2.126×2.146 in)
Compression Ratio 7.4:1 (Corrected) 8.3:1 (Ex valve open); 9.9:1 (Ex valve close)
Displacement 123 cm³ / 7.5 in³ 124 cm³ / 7.6 in³
Horsepower 23 – 26 hp (17 – 19 kW) @ 10,500 RPM 41 hp (30.2 kW) @ 11,500 RPM
Maximum Torque 16.7 Nm (1.7 kgf-m, 12.3 ft-lb) @ 9,500 RPM – RM125M; 17.5 Nm (1.79 kgf-m, 12.9 ft-lb) @ 8,500 RPM – RM125 S 27.1 Nm (2.8 kgf-m, 20.25 ft-lb) @ 10,500 RPM
Top Speed 65 mph (105 km/h)
Air Filtration Wet polyurethane filter Polyurethane foam element
Lubrication Fuel/oil premixture of 20:1 (5%) Fuel/oil premixture of 30:1
Engine Oil & Quantity 750 ml/0.8 US quarts (change); 800 ml/0.8 US quarts (overhaul)
SAE 10W-40 w/ API grade SJ+ meeting JASO MA standards

Drivetrain

An automatic, wet centrifugal clutch system coupled with a chain-and-sprocket mechanism delivered power to the wheels for all RM125 models. Gearing may slightly differ depending on the bike’s model year but still lent to the wheeler’s quick acceleration (the first-year RM125s have straight-cut gears). Transmission-wise, the RM125 originally had a reverse-free 5-speed gearbox that upgraded to a 6-speed constant mesh for later-year versions.

1975 Suzuki RM 125 2006 Suzuki RM 125
Clutch Wet multi-plate, automatic, centrifugal type
Transmission Type 5-speed constant mesh 6-speed constant mesh, return
Gearshift Pattern 1-down, 4-up 1-down, 5-up
Final Drive #428TM chain, 126 links Chain drive DID 520DMA2, 114 links
Primary Reduction Ratio 3.389 (61/18) 3.368 (64/19)
Final Drive Ratio 4.286 (60/14) – solid-mount rear sprocket 4.250 (51/12)
Transfer Gear Ratio Low – 2.143 (30/14)
2nd – 1.588 (27/17)
3rd – 1.250 (25/20)
4th – 1.045 (23/22)
5th – 0.913 (21/23)
Low – 2.071 (29/14)
2nd – 1.687 (27/16)
3rd – 1.444 (26/18)
4th – 1.200 (24/20)
5th – 1.052 (20/19)
Top – 0.950 (19/20)
Yellow Suzuki RM125 Dirt Bike

Ignition

The initial version of the dirt bike had a Pointless Electronic Ignition (PEI), with its CDI unit in front of the air cleaner case when it came out. With the short-lived S model, the CDI unit was made bigger and mounted at the front of the frame headtube with a bracket. Because of the change in CDI placement, it was then possible for the air cleaner case to accommodate a larger rubber connector boot.

As for the battery, the manufacturer did not specify the format recommended for the Suzuki RM125 in the manual. However, you may try if a YTX7L-BS battery would work on the bike. It is the same battery format used on all other Suzuki 125-cc motorcycles. Either that or ask your local dealer what battery fits.

1975 – 2006 Suzuki RM 125
IgnitionElectronic Ignition (CDI)
Ignition Timing5° B.T.D.C @ 1,000 RPM
Spark PlugNGK R6918B-8, 0.55 – 0.65 mm (0.022 – 0.026 in) gap
Torque specs: 17.5 Nm (1.75 kgf-m, 12.5 lb-ft)
GeneratorFlywheel magneto w/ 5-pole stator
Starting SystemPrimary kick
Battery12V 6 Ah/(10 HR) Maintenance-free, YTX7L-BS format
Battery Dimensions114 x 71 x 131 mm (4.50 x 2.81 x 5.19 in)

Tires & Brakes

Front and rear brake size used to be 130 mm and eventually upgraded to 250 mm/240 mm discs. Similarly, stock rubber that came with the two-wheeler changed four times throughout its production run. Front 3.00-21-4PR and rear 3.00-18-4PR tires went on the first RM125 model and lasted until 1979. 1980 to 1985 versions had 90/80-21 (front) and 120/80-18 (rear) tires. The most recent tire sizes are found beginning on ’86 models until ’08 ones. These knobby, MX-style tires mounted on aluminum rims reduced slippage on slick surfaces and provided riders the needed grip on dirt tracks.

1975 – 2006 Suzuki RM 125
Wheel CompositionAluminum
Front TireDunlop® Sports D742F/D756F (non-U.S.) 80/100-21 51M
Rear TireDunlop® Sports D756F 100/90-19 57M
Off-road/road air pressure (F/R)70 – 110 kPa (0.7 – 1.1 kgf/cm2, 10 – 16 psi)
Rim Size (F/R)1.60 × 21 / 1.85 × 19
Tread Depth Limit4 mm (0.16 in)
Front Brake Type250-mm disc brake w/ dual brake calipers, hydraulically operated
Rear Brake Type240-mm disc brake w/ floating brake caliper, hydraulically operated

Suspension

From the get-go, the Suzuki RM 125 provided generous front and rear wheel travel, falling within the 7-to-9-inch range during its first decade. As if that were not enough, the bike introduced the “Full Floater” rear suspension in its 1981 model, one-upping Yamaha in the process.

This suspension system utilized the same rising-rate linkage that most manufacturers already embedded into their motorbike designs at the time. However, its main difference was that it used a floating linkage on the shock absorber’s top and bottom and pull rods that connected the entire system to the swingarm. Thanks to this innovation, later-year versions of the RM125 (and other motocross wheelers) can tackle more technical trails and aggressive jumps.

1975 Suzuki RM 125 2006 Suzuki RM 125
Rake, Trail 61°, 123 mm (7.48 in) 27° 30’, 115 mm (4.53 in)
Steering Angle Refer to ’75 Suzuki RM125 service manual 45° (right & left)
Turning Radius 2.3 m (7.5 ft)
Ground Clearance 245 mm (9.6 in) 350 mm (13.8 in)
Wheelbase 1,360 mm (53.5 in) 1,450 mm (57.1 in)
Front Suspension Type, Travel Telescopic fork, hydraulic damper, 190 mm (7.48 in) Inverted telescopic, pneumatic/coil spring, oil damped, 310 mm (12.2 in)
Rear Suspension Type, Travel Swingarm, hydraulic damper 5-way adjustable spring w/ gas/oil type shocks, 198 mm (7.80 in) Link-type swingarm w/ rebound & compression adjustable gas shocks, 310 mm (12.2 in)

Dimensions & Capacities

There is little difference in overall dimensions and weight across all RM125 models. However, the ’86 model is noteworthy for the enhancements it underwent. Suzuki particularly gave the 1986 RM125G a new and sturdier frame, with some of its parts reduced by almost half.

The “Full Floater rear suspension was retained but with a new swing, an eccentric cam, and a link system (for improved aggressiveness and damping). Interestingly, dry mass is almost virtually unaffected by these changes – not to mention the increase in carb size and other improvements to the chassis and electrical components.

1975 Suzuki RM 1252006 Suzuki RM 125
Length2,040 mm (80.3 in)2,145 mm (84.4 in)
Width860 mm (33.9 in)830 mm (32.7 in)
HeightRefer to ’75 Suzuki RM125 service manual1,275 mm (50.2 in)
Seat Height (Unloaded)901 mm (35.5 in)950 mm (37.4 in)
Dry Weight86 Kg (190 lbs)87 Kg (192 lbs)

Exterior

1976 RM125A models specifically had a chrome-molybdenum profile or Chromoly frames compared to the predominant steel material the rest of the trims and model years had. And while the double-cradle chassis was sturdy enough, further improvements were implemented beginning 2004 – alongside enhancements to the RM125 seat height, brake shave, and suspension system.

1975 – 2006 Suzuki RM 125
FrameSemi double-cradle, Steel
Body MaterialPlastic
Front/Rear Fender FlaresStandard
Upper/Lower FairingN/A
Chain GuardsN/A
Fork GuardsStandard
Skid PlateN/A

On the outside, the bike came standard with handgrips, handlebars, fork guards, and exterior covers but with no lighting whatsoever. Additionally, all Suzuki RM125s models were made available in Champion Yellow. You will need to equip it with a headlight, horn, and turn signals (among other things) if you want to convert your motorbike into a road-legal ride. While you are at it, you can add an Enduro computer kit (view on Amazon) to keep your speed and mileage in check.

How Much Is a RM 125?

Yellow 2004 Suzuki RM125 Dirt Bike

Online resources for pre-2000 RM125 MSRPs are quite difficult to come by. Based on the dirt bike cost in Japan in 1979 (¥255,000), its retail price ranged from $2,290 in the ’70s to $5,099 in 2008. On the other hand, trade-in values range from $85 to $6,305 and can be found on Nada Guides. Interestingly, auction listings are valued higher than trade-in prices and fall between $900 (mainly on Craigslist) and $9,790.

For your reference, the table below shows a full rundown of retail pricing for all RM125 models:

Year – Trim – Model # Retail/Trade-In Values
1975 RM125 N/A
1976 RM125A/S $685 – $4,990
1977 RM125B $685 – $5,635
1978 RM125C $685 – $6,305
1979 RM125 $685 – $5,635
1980 RM125T $685 – $6,305
1981 RM125X $685 – $4,345
1982 RM125Z $685 – $6,305
1983 RM125D
1984 RM125E $685 – $5,635
1985 RM125F $685 – $3,055
1986 RM125G $840 – $4,360
1987 RM125H $685 – $4,140
1988 RM125J $685 – $4,267
1989 RM125K $685 – $4,599
1990 RM125L $685 – $4,099
1991 RM125M $685 – $2,365
1992 RM125N $685 – $3,055
1993 RM125P $685 – $2,365
1994 RM125R
1995 RM125S $225 – $1,560
1996 RM125T $255 – $1,800
1997 RM125V $270 – $1,925
1998 RM125W $350 – $2,085
1999 RM125X $455 – $2,285
2000 RM125Y $610 – $2,795
2001 Suzuki RM125K1 $85 – $3,000
2002 RM125K2 $370 – $490
2003 RM125K3 $405 – $535
2004 RM125K4
2005 RM125K5 $545 – $720
2006 RM125K6 $625 – $820
2007 RM125K7 $680 – $895
2008 RM125K8

Improvements Post-1975

Unlike some of its same-class counterparts, the Suzuki RM125 received a handful of significant mechanical, design, and cosmetic improvements throughout its lifetime – with engine and suspension enhancements being the most popular. Here are noteworthy changes Suzuki did on the motocrosser (Source: U.S. Suzuki Motor Corp. Service Bulletin RM-1, May 1, 1975):

  • 1976 Suzuki RM 125A models were the first in the series to sport an up-swept/high-drawn exhaust pipe, which improved the bike’s competitiveness and speed. Meanwhile, RM 125S models had the pipe drawn under the engine.
  • The 1976 S model got rid of the tall top cap that the M model had, on top of a bigger carburetor size with increased jetting values and angular drilled holes that allowed fuel to bypass the lower needle valve and flow straight into the float bowl.
  • Its engine (RM125S) had a piston valve versus the A model’s reed valve. Also, additional holes were drilled into the piston skirt to aid in cooling the exhaust port bridge section.
  • The RM125S hand-built exhaust pipe comprised rolled steel pieces welded together instead of longitudinal folded seams and was slightly larger in diameter.
  • Introduction of the “Full Floater” swingarm and liquid cooling in 1981
  • Rework of all cylinder barrel ports (by hand)
  • A diameter pipe end with a stiffener rib was welded above and below the bike’s stinger bulb to prevent it from cracking when it met the end of the expansion chamber.
  • Extra L-shaped pieces were put under the bolt heads to hold the end of the springs that kept the head pipe and its chrome exhaust collar in place.
  • RM125B models had a slightly longer leading front axle and muffler. Furthermore, the bore was made slightly smaller and the stroke longer to help with bottom-end performance – ultimately squared off to 54 x 54 mm.
  • The 1986 RM125G had a new power mill that was slimmer and lighter than earlier models. This engine also had a new, flat piston and AEC (Automatic Exhaust Control) system that gave the machine a broader powerband.
  • An 8-mm longer connecting rod, redesigned flat-top piston and exhaust ports, and new exhaust valves made for improved power and torque on mid-high and high RPMs for the RM 125K4 models. To add, a redesigned rear linkage system, thicker front fork, and longer outer fork tube lent to more efficient handling.
  • 2007 versions enjoyed several styling updates, such as race-worthy gripper seats and a redesigned graphic scheme.
  • There was a gradual progression of the fuel tank capacity, horsepower, torque, and speed rating across all models.

About Suzuki

Founded in 1909, Suzuki Motor Corporation did not start its journey in the automotive industry. Instead, its humble beginnings go back to loom weaving in Hamamatsu, Japan. It was not until 1937 that the maker of the Suzuki RM125 considered diversification and decided to build small cars. The company completed this project in 1935 and has not looked back since.

From creating prototype cars, Suzuki moved on to mass-production of motor vehicles, motorcycles, and gas-powered engines. The Japanese firm was also among the first to pioneer the rack-and-pinion steering system. Today, Suzuki is globally renowned as a force to be reckoned with in manufacturing motorcycles, 4WD vehicles, and internal combustion engines.

Conclusion – Suzuki RM 125 Review

For 2-stroke lovers, nothing beats a 125-cc engine on a well-prepped motocross track – and this is exactly what the Suzuki RM125 is. The RM125 has numerous assets and a championship-winning track record that simply cannot be ignored. It is a seriously fun but challenging ride with fewer risks and intimidation that come with higher-displacement bikes. Modded, it becomes a highly capable racer and a formidable adversary on dirt roads. In stock form, it gives a greater feeling of safety that helps boost confidence for riders developing their technique and skills in handling corner speed and overall technical riding.

If you are searching for an aggressive two-wheeler that gives you the best of both worlds (and more), look no further than the classic Suzuki RM 125!

Kris Peter

Adventure seeker and off-road enthusiast. I love the thrill of going off-road and taking on the elements.

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