TM MX 85 (2005-2021): A Pocket Rocket Built for Motocross Domination

When you hear the throaty scream of a two-stroke engine tearing through a motocross track, chances are it’s coming from a machine like the TM MX 85. This Italian-built junior motocross bike has been a staple in the 85cc class for over 15 years, offering a blend of race-ready performance and durability that’s made it a favorite among young riders aiming to climb the competitive ladder. Let’s dive into what makes this motorcycle a standout in its category.

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Overview: The TM MX 85 Legacy

The TM MX 85 Junior isn’t just a motorcycle—it’s a training ground for future champions. Designed for riders aged 12-16 transitioning from mini bikes to full-sized competition machines, this 85cc two-stroke packs a punch that belies its compact size. With minimal changes across its 16-year production run, TM Racing focused on refining an already potent formula rather than reinventing the wheel. The result? A bike that feels purpose-built for aggressive track use while maintaining surprising accessibility for developing riders.

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Engine Performance: Two-Stroke Fury

At the heart of the MX 85 lies a liquid-cooled, single-cylinder two-stroke engine displacing 85cc (5.19 cubic inches). With a bore and stroke of 48mm x 47mm (1.9 x 1.9 inches) and a sky-high compression ratio of 17.2:1, this powerplant is all about explosive mid-range and top-end power delivery.

Key Highlights:
- Carburetion: Earlier models (2005-2015) used Mikuni 28mm carbs, while later iterations switched to Keihin 28mm flat-slide units for crisper throttle response.
- Ignition: Kokusan CDI with variable advance ensures smooth power delivery across the rev range.
- Gearbox: A 6-speed transmission (chain final drive) provides versatility for tight corners and long straights.

Throwing a leg over the MX 85 reveals its true character: unapologetically aggressive. The engine barks to life with a metallic snarl, and the powerband hits like a switchblade once the revs climb past 7,000 RPM. Riders must master clutch modulation (thanks to its hydraulic-controlled multi-disc clutch) to harness the abrupt surge of power—a skill that pays dividends when moving up to larger bikes.

Fuel capacity ranges between 6-9.5 liters (1.59-2.51 US gallons) depending on model year, striking a balance between weight savings and race-length endurance.

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Chassis & Handling: Precision Meets Durability

TM’s commitment to competition shines through in the MX 85’s chassis evolution:
- Frame: Early models used Cr-Mo steel perimetral frames, while 2017+ versions adopted lightweight aluminum perimetral designs for improved stiffness.
- Suspension: A mixed bag across generations. Front forks transitioned from Paioli USD 43mm to Formula 39mm units, while rear shocks ranged from WP to Öhlins and Extreme Tech setups.
- Brakes: Consistent single-disc setups front/rear, with later models boasting premium Brembo/Nissin calipers.

On the track, the MX 85 feels like an extension of the rider’s body. The narrow steel frame (and later aluminum) allows for effortless weight transfer during cornering, while the 17-inch front/14-inch rear wheel combo (70/100-17 front, 90/100-14 rear tires on most models) delivers predictable traction. Suspension tuning leans toward the stiffer side—perfect for hard landings but requiring lighter riders to adjust sag settings.

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Rider Experience: The Good, The Bad, The Italian

Strengths:
- Instantaneous Power: The two-stroke’s hit teaches clutch control and rewards aggressive riding.
- Premium Components: Hydraulic clutch, adjustable suspension, and race-spec brakes outperform many Japanese counterparts.
- Customization: Swappable sprockets, exhausts, and suspension linkages let riders fine-tuning for specific tracks.

Quirks:
- Maintenance Hunger: Typical of high-strung two-strokes—frequent piston replacements and carb tuning are mandatory.
- Steep Learning Curve: Novices might find the powerband intimidating compared to four-strokes.
- Ergonomics: Narrow seat and high pegs favor standing attack positions over casual cruising.

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Competition: How Does It Stack Up?

The 85cc class is fiercely competitive. Here’s how the TM MX 85 battles its rivals:

| Model | Engine | Suspension | Weight | Key Difference |
|--------------------|------------------|----------------------|------------|---------------------------------|
| TM MX 85 | 85cc 2-stroke | Paioli/Öhlins | ~75kg | Hydraulic clutch, race-bred parts |
| KTM 85 SX | 85cc 2-stroke | WP XACT | ~74kg | Softer power delivery |
| Husqvarna TC 85| 85cc 2-stroke | WP XACT | ~75kg | Electric start (later models) |
| Yamaha YZ85* | 85cc 2-stroke | KYB | ~76kg | Budget-friendly, simpler design |

*Estimated dry weight

The TM’s edge lies in its no-compromise racing DNA. While the KTM and Husqvarna offer slightly more user-friendly powerbands, the MX 85’s hydraulic clutch and premium suspension components (like Öhlins shocks on later models) justify its position as a “pro-ready” option. Yamaha’s YZ85, while reliable, can’t match the TM’s component quality but wins in aftermarket support.

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Maintenance: Keeping the Beast Alive

Owning an MX 85 means embracing the two-stroke lifestyle. Here’s your survival guide:

1. Engine Care
- Piston Replacements: Every 15-20 hours for aggressive riders. Opt for forged pistons (Wössner or ProX).
- Carb Tuning: Clean the Keihin/Mikuni carb monthly. Jet changes are common when altitude/temperature shifts.
- Cooling System: Monitor coolant levels religiously—overheating warps cylinders on high-compression engines.

2. Suspension & Chassis
- Fork Seals: Replace annually or after muddy races. Use SKF seals for longevity.
- Linkage Bearings: Grease every 30 hours to prevent corrosion.

3. Brakes
- Brembo/Nissin Upkeep: Bleed hydraulic systems seasonally. Swap sintered pads for better bite.

4. Seasonal Upgrades
- Winter: Fit handguards and softer compound tires.
- Summer: Install high-flow air filters and consider an aftermarket exhaust (FMF or DEP).

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Conclusion: The Coach’s Verdict

The TM MX 85 isn’t just a motorcycle—it’s a mentor. Its unapologetic power delivery teaches discipline, while its race-grade components reward skill development. Yes, it demands more attention than a four-stroke, but for riders serious about motocross, this Italian thoroughbred offers a masterclass in aggressive riding.

Whether you’re rebuilding a 2005 model or tuning a 2021 edition, MOTOPARTS.store has the OEM and aftermarket components to keep your MX 85 at peak performance. From piston kits to suspension linkages, we’ve got your back—because every champion deserves a proper pit crew.

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Specifications sheet

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