TM MX/SM/SMR/SMX/SMM 125: A Legacy of Italian Two-Stroke Mastery (1973-2023)

Introduction

For five decades, TM Racing has crafted some of the most visceral two-stroke experiences on two wheels with its MX/SM/SMR/SMX/SMM 125 series. This Italian thoroughbred defies the industry's shift toward four-strokes, maintaining a cult following among riders who crave the razor-sharp response only a properly tuned 125cc two-stroke can deliver. Whether in motocross trim (MX), supermoto configuration (SMR/SMX), or limited editions like the Black Dream (SMM), these machines scream "race-ready" from every weld. After throwing a leg over a 2020 SMR 125 Fi 2T and a 2019 MX 125 back-to-back, it's clear why this platform remains relevant half a century after its debut.

Design & Ergonomics: Function Over Flair

The TM's aesthetic is unapologetically industrial - a blue-and-white (or murdered-out black on special editions) missile that looks like it rolled straight out of the factory workshop. The aluminum perimeter frame (Cr-Mo steel on early SMM models) forms a skeleton that's both narrower than Japanese rivals and rock-solid at triple-digit lean angles.

Standover height varies between configurations: - MX models: 990mm seat height (39") - SMR supermotos: 920mm (36.2")
That 70mm difference transforms the riding experience - MX versions demand a committed attack stance, while SMRs accommodate quicker weight shifts needed for asphalt antics.

Controls are race-spec minimalism: - No lights, gauges, or frills on MX variants - Brembo radial masters on SMRs deliver surgical brake feel - Footpegs positioned for aggressive weight transfer

Engine Character: Angry Bee Symphony

At the heart beats a 54x54.5mm square-bore two-stroke that's remained fundamentally consistent since the 70s, yet constantly refined: - 123.5cc liquid-cooled single (7.54 cu-in) - V-Force reed valve for crisp throttle response - Keihin PWK 38 carb (or FI on 2023+ models) - Selectable ignition maps via handlebar switch (2016+)

The powerband hits like a caffeine injection - 7.4hp (5.4kW) might sound modest, but in a 96kg (212lb) MX or 100kg (220lb) SMR package, it's explosive. Keep the tach needle dancing between 8,000-11,000 RPM, and you'll outdrag four-strokes twice its displacement.

Key differences between variants: - MX: 5-speed close-ratio box for track assaults - SMR/SMX: 6-speed with taller 5th/6th for road use - Black Dream Editions: Öhlins suspension & Brembo GP4-RS calipers

Chassis & Handling: Scalpel Precision

MX Off-Road Prowess

• Marzocchi/Kayaba USD forks (48mm) with 310mm travel (12.2")
• Sachs/TM Racing shock with 300mm rear travel (11.8")
• 21"/19" spoked wheels shod with knobbies
• 245mm wave rotors (9.6") with Nissin calipers

The MX flicks between ruts with telepathic response. At speed, the chassis remains composed through whoops, though the stiff suspension punishes lazy line choices.

SMR Supermoto Savagery

• 17" cast wheels with 120/70-17 front, 150/60-17 rear
• Brembo radial brakes with 320mm front rotor (12.6")
• Shorter suspension travel (280mm front/270mm rear)
• 27° rake for quicker steering than MX models

On twisty tarmac, the SMR transforms into a knee-dragging hooligan. The front Bridgestone Battlax bites hard enough to lift the rear wheel under trail braking. Transitioning between hairpins feels like steering with your hips - intuitive and immediate.

Competition: How TM Stacks Up

Motocross Arena (MX 125)

• KTM 125 SX: More peak power (14hp) but vaguer chassis feel
• Husqvarna TC 125: Comparable agility, less durable transmission
• Yamaha YZ125: Softer power delivery, dated suspension

TM's Edge: Customization. While orange bikes dominate dealer networks, TM offers factory-backed engine kits and geometry adjustments that turn the MX into a specialist weapon.

Supermoto Battleground (SMR/SMX)

• Aprilia SX 125: Road legal but 20kg heavier
• Beta RR 125 LC: Better low-end, less top-end scream
• Husqvarna SMS 125: Four-stroke tractability, two-stroke boredom

TM's Ace Card: The 2023 SMR 125 Fi 2T's fuel injection eliminates carb tuning headaches that plague rivals during altitude changes - crucial for alpine road warriors.

Maintenance: Keeping the Italian Stallion Galloping

Two-Stroke Specifics

1. Top-End Rebuilds: Every 40-60 hours for MX race use, 100hrs for casual SMR riding. MOTOPARTS.store stocks Vertex pistons kits ($189) with gaskets.
2. Oil Mix: 3.5% (40:1) with full synthetic. Bel-Ray H1R ($18/liter) prevents powervalve gunk.
3. Carb Tuning: JD Jet Kits ($75) simplify altitude/temperature adjustments on pre-2023 models.
4. Cooling: TM-specific silicone hoses ($129/set) improve durability over stock rubber.

Chassis Upkeep

• Suspension Service: Sachs shock rebuild kits ($89) every 50hrs
• Brakes: SBS 615 sintered pads ($45) outperform OEM in mud
• Chain: DID 520ERV3 ($125) lasts 30% longer than stock

MODOPARTS.store Pro Tips

• Upgrade MX pegs to Raptor Titanium ($199) for better mud clearance
• SMR riders love the Domino XM2 quick-turn throttle ($65)
• All models benefit from Boyesen Supercooler kits ($149)

The Verdict: An Addiction in Blue and White

The TM 125 series isn't for everyone - it demands mechanical sympathy, rewards aggressive riding, and punishes complacency. But for those willing to learn its ways, few bikes offer this level of tactile feedback. The MX variant remains a dark horse in amateur motocross, while the SMR/SMX continues embarrassing liter bikes on canyon roads.

Fifty years of evolution have refined without diluting - a testament to TM's mad-scientist approach. As emission laws strangle two-strokes globally, these Italian terriers remind us why we fell in love with motorcycling's rawest era. Ride one, and you'll either walk away baffled... or start browsing TM's factory race kits.

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Specifications sheet

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