Honda Monkey 125 4-Speed (JB02) — OEM Fluid, Tire Pressure & Maintenance Specs
125cc Air-Cooled Horizontal Single SOHC 2V 4-Speed Manual · Source: Honda Monkey 125 4-Speed (JB02) (2018–2021) Official Owner’s Manual Maintenance Specifications
According to the Honda Monkey 125 4-Speed (JB02) (2018–2021) Official Owner’s Manual Maintenance Specifications, the 2018–2021 Honda Monkey 125 4-Speed (JB02) (chassis JB02) requires 0.9 L (0.95 US qt) of SAE 10W-30 (JASO MA, API SJ or higher) engine oil for a drain-only change and 0.9 L (0.95 US qt) with filter service (15421-KSP-910 (Screen + Centrifugal Spinner)). Standard solo cold tire pressure is 200 kPa / 2.00 bar / 29 PSI front (120/80-12 65J) and 200 kPa / 2.00 bar / 29 PSI rear (130/80-12 69J), paired with 1× NGK CPR6EA-9S spark plug(s) and a YTZ5S battery.
Drain only: 0.9 L (0.95 US qt)
R 200 kPa (2.00 bar)
Est. Range: ~336 km (209 mi)
1. Engine Lubrication, Filter & Clutch Specifications
| Clutch Architecture | Wet Multi-Plate Manual Clutch NEVER use JASO MB |
|---|---|
| Recommended Viscosity & Grade | SAE 10W-30 (Alt: SAE 10W-40) · JASO MA · API SJ 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: 1.1 L (1.16 US qt) |
| OEM Oil Filter Code & Type | 15421-KSP-910 (Screen + Centrifugal Spinner) |
| Correct Oil Level Check Method | Hold upright on level ground; rest dipstick UNTHREADED on filler neck (do NOT screw in) |
| Oil Drain Bolt Torque | 24 N·m (17.7 lb-ft / 2.45 kgf·m) — Use fresh crush washer |
2. Cold Tire Pressures, Wheels, Ignition & Drivetrain
| Front / Rear OEM Tire Sizes | Front: 120/80-12 65J · Rear: 130/80-12 69J (Tubeless) |
|---|---|
| Cold Tire Pressure — Solo Riding |
Front: 200 kPa / 2.00 bar / 29 PSI Rear: 200 kPa / 2.00 bar / 29 PSI |
| Cold Tire Pressure — 2-Up / Loaded Touring |
Front: 200 kPa / 2.00 bar / 29 PSI Rear: 200 kPa / 2.00 bar / 29 PSI |
| OEM Spark Plug & Quantity | NGK CPR6EA-9S × 1 (Gap: 0.8–0.9 mm) |
| OEM Battery Code & Rating | YTZ5S (12V 3.5Ah MF AGM) |
| Final Drive Maintenance | 428 Drive Chain — Maintain 20–30 mm slack and lubricate regularly |
| Brake Fluid & Coolant | DOT 4 · Air/Oil-Cooled Engine (No liquid coolant) |
3. Ergonomics, Range & Scheduled Service Intervals
| Displacement · Max Power · Peak Torque | 125 cc · 9.4 hp @ 7,000 rpm · 11 N·m (8.1 lb-ft) @ 5,250 rpm |
|---|---|
| Seat Height & Wet Curb Weight | 775 mm (30.5 in) · 107 kg (236 lbs) |
| Fuel Tank & Est. Real-World Range | 5.6 L (1.5 US gal) · ~60 km/L → ~336 km (209 mi) |
| OEM Scheduled Maintenance Intervals |
• First Break-In: 1,000 km • Engine Oil / Filter: 6,000 km / 12,000 km • Air Filter / Spark Plug: 16,000 km / 12,000 km • Valve Clearance Check: 8,000 km |
4. Generation Cutoffs & Real-World Wrenching Gotchas
Model-Year & Chassis Generation Notes
Visually almost identical to the 2022+ 5-speed JB03, but the 2018–2021 4-speed JB02 uses a centrifugal spinner with NO cartridge paper oil filter.
Oil & Clutch Mechanical Engineering Note
Honda air-cooled manual-clutch mini-moto single requiring SAE 10W-30 JASO MA oil and periodic filter/centrifugal spinner service.