Yamaha SR400 Carburetor (1JR / RH01J) — OEM Fluid, Tire Pressure & Maintenance Specs
399cc Air-Cooled Single SOHC 2-Valve Carburetor (Frame Dry-Sump) · Source: Yamaha SR400 Carburetor (1JR / RH01J) (1978–2008) Official Owner’s Manual Maintenance Specifications
According to the Yamaha SR400 Carburetor (1JR / RH01J) (1978–2008) Official Owner’s Manual Maintenance Specifications, the 1978–2008 Yamaha SR400 Carburetor (1JR / RH01J) (chassis 2H6/1JR/RH01J) requires 2 L (2.11 US qt) of SAE 10W-40 (JASO MA2, API SG or higher) engine oil for a drain-only change and 2.1 L (2.22 US qt) with filter service (4X7-13440-90 / HF145). Standard solo cold tire pressure is 175 kPa / 1.75 bar / 25 PSI front (90/100-18M/C 54S) and 200 kPa / 2.00 bar / 29 PSI rear (110/90-18M/C 61S), paired with 1× NGK BPR6ES spark plug(s) and a GT4B-5 battery.
Drain only: 2 L (2.11 US qt)
R 200 kPa (2.00 bar)
Est. Range: ~312 km (194 mi)
1. Engine Lubrication, Filter & Clutch Specifications
| Clutch Architecture | Wet Multi-Plate Manual Clutch NEVER use JASO MB |
|---|---|
| Recommended Viscosity & Grade | SAE 10W-40 (Alt: SAE 20W-40 / 15W-50) · JASO MA2 · API SG or higher |
| Oil Volume (Drain / With Filter / Overhaul) |
• Drain only: 2 L (2.11 US qt) • With filter/strainer: 2.1 L (2.22 US qt) • Complete dry overhaul: 2.4 L (2.54 US qt) |
| OEM Oil Filter Code & Type | 4X7-13440-90 / HF145 |
| Correct Oil Level Check Method | Dry-sump oil tank — warm engine to operating temperature and check oil tank/frame dipstick immediately after shutdown per OEM procedure (never top up cold) |
| Oil Drain Bolt Torque | 30 N·m (22.1 lb-ft / 3.06 kgf·m) — Use fresh crush washer |
2. Cold Tire Pressures, Wheels, Ignition & Drivetrain
| Front / Rear OEM Tire Sizes | Front: 90/100-18M/C 54S · Rear: 110/90-18M/C 61S (Tube-Type Spoke Rim) |
|---|---|
| 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: 200 kPa / 2.00 bar / 29 PSI Rear: 225 kPa / 2.25 bar / 33 PSI |
| OEM Spark Plug & Quantity | NGK BPR6ES × 1 (Gap: 0.7–0.8 mm) |
| OEM Battery Code & Rating | GT4B-5 (12V 2.5Ah Sealed (Kickstart)) |
| 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 | 399 cc · 27 hp @ 7,000 rpm · 29 N·m (21.4 lb-ft) @ 6,500 rpm |
|---|---|
| Seat Height & Wet Curb Weight | 785 mm (30.9 in) · 168 kg (370 lbs) |
| Fuel Tank & Est. Real-World Range | 12 L (3.2 US gal) · ~26 km/L → ~312 km (194 mi) |
| OEM Scheduled Maintenance Intervals |
• First Break-In: 1,000 km • Engine Oil / Filter: 5,000 km / 10,000 km • Air Filter / Spark Plug: 15,000 km / 10,000 km • Valve Clearance Check: 10,000 km |
4. Generation Cutoffs & Real-World Wrenching Gotchas
Model-Year & Chassis Generation Notes
Spanning the beloved drum-front 1985–2000 1JR era and the 2001–2008 RH01J era (returning to a right-hand front disc and Mikuni BSR34 CV carb), prior to 2010 fuel injection.
Oil & Clutch Mechanical Engineering Note
Drain both the downtube frame plug and engine sump plug, replace paper element HF145, and refill 2.1 L of SAE 10W-40 or classic 20W-40/15W-50 JASO MA2 oil.