MZ 660 Mastiff [1998-2007]: The Unconventional Thumper That Defies Expectations

When you first lay eyes on the MZ 660 Mastiff, it’s hard to pin down its personality. Is it a rugged enduro warrior? A street-smart supermoto? Or a minimalist naked bike that prioritizes function over flair? The answer, as I discovered during a week-long test ride of a meticulously maintained 2003 model, is all of the above – and none of them. This German-engineered machine carves its own niche in the motorcycle world, blending industrial charm with surprising versatility.

The Heart of the Beast: A 660cc Liquid-Cooled Thumper

At the core of the Mastiff lies its defining feature – a 660cc single-cylinder engine that delivers character by the bucketload. The liquid-cooled mill produces between 37-50 HP (depending on model year and tuning) with a meaty 57 Nm (42 lb-ft) of torque that arrives early at 5,250 RPM. While these numbers might not set modern spreadsheets ablaze, the reality of riding this big single is far more engaging than spec sheets suggest.

Key riding impressions: - The engine vibration spectrum ranges from "therapeutic massage" at idle to "jazz hands symphony" near redline - Torque delivery feels agricultural in the best possible way – like a tractor that suddenly decided to take up canyon carving - Exhaust note oscillates between industrial percussion and deep, throaty braap depending on throttle input

The 5-speed transmission shifts with deliberate mechanical clicks, rewarding positive foot action but punishing half-hearted gestures. Cruising at 100 km/h (62 mph) sees the engine spinning at a relaxed 4,500 RPM, though the lack of a sixth gear makes extended highway runs feel like you’re constantly negotiating with physics.

Chassis Dynamics: Schrödinger's Motorcycle

The Mastiff’s identity crisis becomes its greatest strength when the road gets interesting. With a wheelbase of 1,465 mm (57.7"), it threads through tight corners like a trials bike yet maintains surprising stability at speed. The adjustable 190mm (7.5") suspension travel front and rear transforms based on your mission:

• Street mode: Slightly overdamped for aggressive pavement scratching
• Fire road setting: Revels in swallowing mid-sized bumps like a hungover college student at a breakfast buffet
• Urban assault configuration: Turns curbs into launch pads with cartoonish enthusiasm

The 830mm (32.7") seat height looks intimidating on paper but actually accommodates most riders thanks to narrow ergonomics. After three hours in the saddle, your posterior will remind you this is no Gold Wing – but the upright riding position keeps fatigue at bay longer than expected.

Braking Performance: Adequate with Personality

The single 245mm discs front and rear deliver stopping power that’s best described as "enthusiastically sufficient." Initial bite lacks the immediacy of modern radial setups, but there’s a lovely progression to the lever feel that rewards skilled riders. In wet conditions, the brakes transform into philosophical objects – they’ll make you contemplate the nature of momentum and friction while gently reminding you to leave bigger gaps.

The Shape-Shifting Experience

Urban Jungle: Filtering through traffic becomes a game of "how narrow can we go?" The high vantage point and narrow profile make bicycle messengers nod in respect. Fuel consumption of 5.8 L/100km (40.5 mpg) means you’ll be counting gas station visits on one hand.

Backroad Blitz: Push hard into a corner and the Mastiff responds with playful rear wheel slides that feel more intentional than alarming. The 150/60-17 rear tire communicates through seat vibrations rather than subtle feedback – it’s like riding a telegram from your contact patches.

Off-Piste Adventures: While no KTM 690 Enduro R, the Mastiff handles light trails with gruff competence. Ground clearance becomes limiting before suspension does, and the 179kg (394.6 lb) wet weight feels more manageable in motion than on the spec sheet.

Competition: The Underdog’s Playground

Against contemporaries like the Suzuki DR650, Honda XR650L, and KTM 640 Adventure, the Mastiff carves its niche:

• Versatility: Out-pavements the DR650, out-dirtroads the SV650
• Character: Makes Japanese rivals feel like appliances by comparison
• Custom Potential: The blank-canvas design begs for personalization (more on that later)

Where it stumbles: - Refinement: The KTM 640 runs circles around it in technical terrain - Aftermarket Support: Requires more creativity than Honda’s plug-and-play ecosystem - Weight Distribution: Carries its 175kg (385.8 lb) dry weight higher than a yoga instructor’s self-esteem

Maintenance: Keeping the Beast Happy

As MOTOPARTS.store’s resident wrench-spinner, I can confirm the Mastiff rewards diligent owners. Key considerations:

1. Valve Adjustments: Every 10,000 km (6,200 miles) for the 5-valve head. Our ProX Valve Shim Kits make this dentist-level precision work slightly less terrifying.

2. Carburetor TLC: Later fuel-injected models avoid this, but carbureted versions benefit from our All-Balls Carb Rebuild Kits. Pro tip: Carry spare jets if you frequently change elevations.

3. Chain & Sprockets: The O-ring chain lasts 20,000 km (12,400 miles) with proper care. Our RK XSO-Ring Chain + JT Sprocket kits add longevity for high-mileage riders.

4. Suspension Refresh: The WP Suspension Seal Head Kits breathe new life into tired forks. For serious off-roaders, consider upgrading to Hyperpro Progressive Springs.

5. Electrical Quirks: Our Mosfet Regulator/Rectifier units solve 80% of charging issues. Pair with a Motobatt MBTX12U battery for worry-free starts.

The MOTOPARTS.store Upgrade Path

Transform your Mastiff from quirky to killer with these proven mods:

1. Exhaust Enlightenment: The LeoVince X3 Slip-On reduces weight by 3kg (6.6 lbs) and unlocks the engine’s hidden voice – imagine a baritone didgeridoo.

2. Lighting Revolution: Our Denali D4 2.0 LED Kit turns night riding into a daylight simulation experience.

3. Ergo Upgrade: Rox 2" Pivoting Risers combined with a Seat Concepts Comfort XL transforms all-day comfort from myth to reality.

4. Tire Freedom: Swap to Pirelli Scorpion Rally STRs (120/70-19 front, 150/70-17 rear) for true 50/50 capability.

5. Crash Protection: Our Hepco & Becker Engine Guards add peace of mind with style points deducted.

Living With the Mastiff: Quirks and Charms

Ownership is a relationship rather than a transaction. You’ll learn to:

• Interpret various oil seepages as "character marks" rather than defects
• Develop ESP for finding neutral (hint: it’s always when you’re not looking)
• Appreciate the minimalist dash as a digital detox experience
• Master the art of explaining "Yes, MZ still exists" to curious onlookers

The Verdict: Cult Classic Material

The MZ 660 Mastiff won’t coddle you with refinement or stroke your ego with prestige. What it offers is raw, mechanical authenticity in an increasingly sanitized two-wheeled world. It’s the motorcycle equivalent of a hand-forged chef’s knife – requires skill to master, rewards patience, and becomes irreplaceable once understood.

For riders seeking: - A blank canvas for mechanical self-expression - Therapy sessions replaced by valve adjustments - Conversations starters at every gas stop - The joy of owning something truly different

...the Mastiff delivers in spades. Just keep our phone number handy for those "I’m gonna try something" moments – we’ve got the parts and expertise to keep your German oddball running right.

About the author: A MOTOPARTS.store staff writer who may or may not have traded a kidney for a low-mileage Mastiff project bike after this test ride.

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Specifications sheet

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