Yamaha Cygnus-X 125 (SEA5J / SED8J) — OEM Fluid, Tire Pressure & Maintenance Specs
124cc Forced Air-Cooled Single SOHC 4-Valve FI (Dual-Disc 12-Inch) · Source: Yamaha Cygnus-X 125 (SEA5J / SED8J) (2015–2020) Official Owner’s Manual Maintenance Specifications
According to the Yamaha Cygnus-X 125 (SEA5J / SED8J) (2015–2020) Official Owner’s Manual Maintenance Specifications, the 2015–2020 Yamaha Cygnus-X 125 (SEA5J / SED8J) (chassis SEA5J/SED8J/BF9/B8S) requires 0.9 L (0.95 US qt) of SAE 10W-40 (JASO MB, API SG or higher) engine oil for a drain-only change and 0.9 L (0.95 US qt) with filter service (B65-E3411-00 (Oil Strainer Screen)). Standard solo cold tire pressure is 175 kPa / 1.75 bar / 25 PSI front (110/70-12 47L) and 200 kPa / 2.00 bar / 29 PSI rear (120/70-12 51L), paired with 1× NGK CR7E spark plug(s) and a YTZ7V / YTZ6V battery.
Drain only: 0.9 L (0.95 US qt)
R 200 kPa (2.00 bar)
Est. Range: ~241 km (150 mi)
1. Engine Lubrication, Filter & Clutch Specifications
| Clutch Architecture | Dry Centrifugal CVT Belt Drive |
|---|---|
| Recommended Viscosity & Grade | SAE 10W-40 (Alt: SAE 10W-30) · JASO MB · API SG or higher |
| Oil Volume (Drain / With Filter / Overhaul) |
• Drain only: 0.9 L (0.95 US qt) • With filter/strainer: 0.9 L (0.95 US qt) • Complete dry overhaul: 1 L (1.06 US qt) |
| OEM Oil Filter Code & Type | B65-E3411-00 (Oil Strainer Screen) |
| Correct Oil Level Check Method | Hold upright on level ground; rest dipstick UNTHREADED on filler neck (do NOT screw in) |
| Oil Drain Bolt Torque | 20 N·m (14.8 lb-ft / 2.04 kgf·m) — Use fresh crush washer |
| Final Drive / Bevel Gear Oil | 110 ml (0.11 L) — SAE 10W-40 / 85W-140 (110 ml rear gear oil) |
2. Cold Tire Pressures, Wheels, Ignition & Drivetrain
| Front / Rear OEM Tire Sizes | Front: 110/70-12 47L · Rear: 120/70-12 51L (Tubeless) |
|---|---|
| Cold Tire Pressure — Solo Riding |
Front: 175 kPa / 1.75 bar / 25 PSI Rear: 200 kPa / 2.00 bar / 29 PSI |
| Cold Tire Pressure — 2-Up / Loaded Touring |
Front: 175 kPa / 1.75 bar / 25 PSI Rear: 225 kPa / 2.25 bar / 33 PSI |
| OEM Spark Plug & Quantity | NGK CR7E × 1 (Gap: 0.8–0.9 mm) |
| OEM Battery Code & Rating | YTZ7V / YTZ6V (12V 6.0Ah MF AGM) |
| Final Drive Maintenance | Dry V-Belt CVT Drive — Inspect/replace V-belt and rollers every 20,000–24,000 km |
| Brake Fluid & Coolant | DOT 4 · Forced Air-Cooled Engine (No liquid coolant) |
3. Ergonomics, Range & Scheduled Service Intervals
| Displacement · Max Power · Peak Torque | 124 cc · 9.8 hp @ 7,500 rpm · 9.9 N·m (7.3 lb-ft) @ 6,000 rpm |
|---|---|
| Seat Height & Wet Curb Weight | 775 mm (30.5 in) · 119 kg (262 lbs) |
| Fuel Tank & Est. Real-World Range | 6.5 L (1.7 US gal) · ~37 km/L → ~241 km (150 mi) |
| OEM Scheduled Maintenance Intervals |
• First Break-In: 1,000 km • Engine Oil / Filter: 4,000 km / 8,000 km • Air Filter / Spark Plug: 12,000 km / 8,000 km • Valve Clearance Check: 12,000 km |
4. Generation Cutoffs & Real-World Wrenching Gotchas
Model-Year & Chassis Generation Notes
Spanning the 2015–2017 4th-gen (SEA5J/BF9, adding a rear disc) and 2018–2020 5th-gen (SED8J/B8S, adding LED lighting and ABS), this was the final air-cooled Cygnus-X.
Oil & Clutch Mechanical Engineering Note
Running a high-revving forced-air-cooled 4-valve DiASil/ceramic cylinder without liquid cooling, refresh its 0.9 L of SAE 10W-40 JASO MB synthetic oil every 2,000–2,500 km.
Garage Wrenching Gotchas
- Lubricate the O-ring on the large aluminum lower strainer cap and thread it by hand before torquing to 20 N·m; cross-threading or pinching the O-ring dumps the 0.9 L sump rapidly.
- Because the fuel filler neck sits on the front legshield apron, avoid topping past the auto-shutoff click so fuel expansion does not stain painted trim.
5. Frequently Asked Questions (FAQ)
What are the engine oil and rear hub gear oil capacities for the Yamaha Cygnus-X 125 (SEA5J / SED8J) scooter?
With an isolated dry CVT belt case, the engine requires 0.9 L drain-only or 0.9 L (0.95 US qt) with filter/screen (B65-E3411-00 (Oil Strainer Screen)) of SAE 10W-40 (JASO MB). Service the rear reduction hub separately (final drive 110 ml).
How do you accurately check the oil level on the Cygnus-X 125 (SEA5J / SED8J), and what are its service intervals?
Hold the bike upright on level ground 2–3 minutes after shutdown, wipe the dipstick, and rest it on the filler threads without screwing it in (threading it in reads artificially high and risks oil starvation). Torque the drain plug to 20 N·m with a new crush washer. Factory oil change intervals are every 4,000 km, with valve clearance inspection every 12,000 km.
What are the cold tire pressures, puncture repair type, seat height, and range of the Cygnus-X 125 (SEA5J / SED8J)?
Fitted with 110/70-12 47L front and 120/70-12 51L rear tubeless rims (compatible with roadside plug kits), set cold tire pressures to 25 / 29 PSI (175/200 kPa) solo or 25 / 33 PSI loaded. Seat height is 775 mm (30.5 in) at 119 kg wet weight, delivering ~241 km per 6.5 L tank.