Yamaha YZ250 (2017-2021): A Two-Stroke Legend Refined for Modern Motocross

Introduction

The Yamaha YZ250 has long been the torchbearer of two-stroke motocross glory, and the 2017–2021 iteration proves why this bike remains a cult favorite. While the industry shifted toward four-strokes, Yamaha doubled down on refining its iconic two-stroke platform. This generation isn’t about reinvention—it’s about perfecting a formula that balances raw power, lightweight agility, and rider-friendly mechanics. After a day of thrashing this machine on everything from hardpack tracks to sandy whoops, it’s clear why riders still swear by the YZ250’s visceral charm.

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Engine Performance: The Heartbeat of a Two-Stroke Purist

At the core of the YZ250 lies its 249cc liquid-cooled two-stroke engine, unchanged in displacement but meticulously tuned for responsiveness. The Keihin PWK38S carburetor delivers crisp throttle response, and while fuel injection dominates modern bikes, there’s an undeniable satisfaction in dialing in the air screw (set at 2.25 turns out from factory) for perfect jetting.

Power Delivery:
The engine’s character is unapologetically aggressive. From mid-range to top-end, the YZ250 pulls with a ferocity that four-strokes struggle to match. The 10.6:1 compression ratio ensures a hard-hitting powerband, but the reed-valve induction system softens the hit just enough to keep the rear wheel hooked up. Riders can expect 48–52 horsepower (depending on tuning), which translates to explosive acceleration out of corners and effortless clears on big jumps.

Two-Stroke Quirks:
Premixing fuel (30:1 is Yamaha’s recommendation) becomes second nature, and the ritual feels like a small price to pay for the engine’s simplicity. The CDI ignition system fires up reliably with the electric starter—a luxury not all two-strokes offer—though kicking it over manually (just in case) still feels nostalgic.

Cooling & Reliability:
The liquid-cooling system (1.2L capacity) works overtime on technical trails, but it never faltered during testing. Riders in muddy conditions will appreciate the fork guards’ extra coverage, preventing sludge from caking the radiators.

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Chassis & Handling: Precision Meets Durability

The aluminum semi-double cradle frame is a masterpiece of flex and rigidity. At 103 kg (227 lbs) wet, the YZ250 feels flickable mid-air and planted in ruts. The 1,481 mm (58.3") wheelbase strikes a balance between stability at speed and agility in tight sections.

Suspension Setup:
KYB’s Speed-Sensitive System (SSS) forks are the star here. With 300 mm (11.8") of travel and 48mm stanchions, they absorb square-edged hits like a sponge while remaining supportive on landings. The rear KYB shock mirrors this performance, offering 315 mm (12.4") of travel with minimal fade even after consecutive motos.

Adjustability:
Both ends are fully adjustable. For intermediate riders, starting at 12 clicks out on compression (front) and 10 clicks (rear) provides a plush feel. Faster riders might stiffen the compression by 3–4 clicks for added track precision.

Tires & Brakes:
The Dunlop MX52 tires (80/100-21 front, 110/90-19 rear) are predictable across varied terrain, though hardpack riders might swap to a MX33 for sharper edges. The 245mm front and rear discs lack the initial bite of Brembos but offer progressive modulation—ideal for maintaining corner speed.

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Ergonomics: Built for Attack

Yamaha’s "rider triangle" on this generation emphasizes control. The 970 mm (38.2") seat height feels accessible for riders as short as 5’6" (168 cm), while the narrow frame allows taller riders to grip the bike with their knees effortlessly.

Handling the Weight:
At 103 kg (227 lbs), the YZ250 disappears beneath you once moving. The weight distribution leans slightly forward, which helps keep the front end planted during aggressive corner entries. Standing up through choppy sections feels natural, thanks to the flat seat-to-peg relationship.

Controls & Comfort:
The Renthal Fatbar (971 bend) offers a neutral grip position, reducing arm pump during long motos. The clutch pull is featherlight—a surprise for a cable-actuated system—and the 5-speed transmission shifts with a satisfyingly positive click.

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Competition: How the YZ250 Stacks Up

KTM 250 SX

KTM’s two-stroke rival weighs slightly less (99 kg / 218 lbs) and boasts a hydraulic clutch. However, the YZ250’s suspension is more forgiving on rough tracks, and Yamaha’s aftermarket support (like our MOTOPARTS.store catalog) is broader for budget-conscious riders.

Honda CRF250R

Honda’s four-stroke leans into tractable power and fuel injection. But at 106 kg (234 lbs), it feels heavier in the air, and maintenance costs (valve adjustments, timing chains) add up. The YZ250’s simplicity and lower rebuild costs make it a winner for privateers.

Husqvarna TC 250

Husky’s two-stroke shares KTM’s DNA but adds a composite subframe. It’s a worthy competitor, though the YZ250’s steel footpegs and gripper seat offer better durability for aggressive riders.

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Maintenance: Keeping the YZ250 in Fighting Shape

Two-Stroke Essentials

• Premix Ratio: Stick to 30:1 with high-quality synthetic oil. For colder climates, a 32:1 ratio reduces spooge.
• Spark Plugs: The NGK BR8EG is reliable, but the iridium BR8EIX (0.5–0.6 mm gap) lasts longer under heavy load.
• Air Filter: Clean every 3–5 hours. Use no-rinse cleaners for quicker service.

Suspension & Chassis

• Fork Oil: Replace every 40 hours. Yamaha recommends 10W-40 oil for the forks, but many riders switch to KYB 01M fluid for smoother action.
• Chain: The 520 chain lasts ~20 hours in sandy conditions. Pair with aftermarket steel sprockets (14/50 gearing) from MOTOPARTS.store for longevity.

Cooling & Brakes

• Coolant: Replace annually with ethylene glycol-based fluid. Check for leaks at the pump seal after deep pressure washes.
• Brake Fluid: Flush DOT 4 fluid every 60 hours. Stainless steel brake lines (available in our store) improve lever feel.

Pro Tips from MOTOPARTS.store

• Upgrade to a VForce4 reed valve for sharper throttle response.
• Install a skid plate if you’re tackling rocky trails.
• Swap the stock grips for ODI lock-ons to reduce vibration.

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Final Thoughts

The 2017–2021 Yamaha YZ250 isn’t just a relic—it’s a testament to the staying power of two-stroke engineering. Whether you’re a vet rider chasing nostalgia or a young gun learning throttle control, this bike rewards skill and punishes complacency. Its aftermarket-friendly design means every component can be tailored to your style, and with MOTOPARTS.store’s extensive catalog, optimizing your YZ250 is just a click away.

Two-strokes may no longer rule the podium, but the YZ250’s howling exhaust note and razor-sharp handling ensure it’ll always rule the dirt.

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Specifications sheet

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