The facts.
| Brand | STM |
|---|---|
| Part number | FYA-S140 |
| Type | Slipper clutch (anti-hopping clutch) |
| Fitment | Yamaha YZF-R1 (2009–2014) |
| Anti-hopping mechanism | Patented ball-ramp system |
| Spring type | Diaphragm spring |
| Weight saving | Approximately 0.7–0.8 kg (rotating mass reduction vs. stock) |
| Intended use | Track and high-performance road riding |
DescriptionThe whole story▼
On the track, the margin between a fast lap and a highside is measured in milliseconds. The STM slipper clutch for the Yamaha YZF-R1 (2009-2014) closes that margin decisively — eliminating rear-wheel hop under hard braking and aggressive downshifts so you can trail-brake later, slide the rear with confidence, and carry more corner speed every single lap.
Key Features
- Prevents engine over-rev on downshifts, delivering a stable, controlled deceleration phase without rear-wheel chatter
- Significantly reduces rear-wheel hop, improving traction and stability under the heaviest braking
- Lowers the trigger impulse of a highside, increasing safety at race and road speeds alike
- Enables controlled rear-wheel slides for sharper, more progressive cornering and improved feel
- Refined clutch closing phase in corners actively prevents the front-end tuck associated with abrupt engine braking
- Diaphragm spring design eliminates pressure-plate flutter, giving the lever a smooth, consistent release feel
- Patented ball-ramp mechanism governs the anti-hopping function with precision across the entire rev range
- Weight saving of approximately 0.7–0.8 kg through reduced rotating mass, directly improving throttle response and acceleration
Engineering Behind the Design
STM's ball-ramp anti-hopping system is a genuine racing solution adapted for the street-legal YZF-R1. When the engine overruns the rear wheel — the scenario that causes rear-wheel hop and, at its worst, a highside — the ramp mechanism partially disengages the clutch pack, allowing the rear tyre to maintain contact with the road and the rider to stay in control. The moment drive is reapplied, the clutch re-engages seamlessly, with no lag and no drama.
The diaphragm spring replaces the conventional coil-spring arrangement, smoothing out pressure-plate movement and giving the clutch lever a progressive, linear feel that long-distance and track riders alike will appreciate after an hour of hard riding.
Performance Gains on Track and Road
The reduction in rotating mass — roughly 0.7 to 0.8 kg — is one of the less-discussed advantages of the STM unit. On a machine as responsive as the YZF-R1, that saving translates into crisper throttle response and marginally faster acceleration out of slow corners. Combined with the anti-hopping behaviour, the result is a clutch that actively makes you faster rather than simply transmitting power.
Fitment & Compatibility
This clutch is a direct, application-specific fit for the following models:
- Yamaha YZF-R1 — 2009, 2010, 2011, 2012, 2013, 2014
Part number FYA-S140 is unique to this fitment. Always verify your model year and variant before ordering.
Specifications
- Brand: STM
- Part number: FYA-S140
- Type: Slipper clutch (anti-hopping clutch)
- Fitment: Yamaha YZF-R1 (2009–2014)
- Anti-hopping mechanism: Patented ball-ramp system
- Spring type: Diaphragm spring
- Weight saving: approximately 0.7–0.8 kg vs. stock (rotating mass reduction)
- Intended use: Track and high-performance road riding
FitmentWhich bikes this fits▼
- Yamaha YZF-R1 (2009–2014)
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