Yamaha DT 400 MX (1977–1980) — Specs
Identity
Manufacturer: Yamaha
Model: DT 400 MX
Category: Motorcycle
Type: Motorcycle
Years: 1977 → 1980
Engine
Displacement (cc): 397
Cylinders: 1
Power (hp): 20
Power (kW): 15
Torque (Nm): 38
Dimensions
Overall length: 2100 mm
Overall width: 790 mm
Overall height: 1140 mm
Wheelbase: 1430 mm
Ground clearance: 160 mm
Weight (kg): 139
Tank (L): 9
Tires
Front tire: 3.00-21
Rear tire: 4.00-18
Front pressure (bar): 1.8
Rear pressure (bar): 2
Drivetrain
Drive chain: 520 chain, 102 links
Sprockets (front / rear): 17 / 42
Ignition
Spark plug: NGK B8ES
Plug gap: 0.8 mm
Fluids & Filters
Air filter: OEM air filter
Brake fluid: DOT 4
Fuel consumption
Estimated fuel consumption: ~4.0 L/100 km
Estimated range: ~225 km on a full tank (9.0 L)
Note: estimate based on engine size + bike type. Real-world ±20%.
Service
Battery: OEM battery specification
Service interval (km): 3000
Service interval (months): 12
Parts and consumables for this motorcycle
Data is gathered with care, but without guarantee. Always confirm critical information with your dealer or workshop.
Service notes
Service interval: every 3,000 km or 12 months, whichever comes first. Spark plug: NGK B8ES (gap 0.8 mm). Chain: 102 links, sprockets 17/42 teeth. Tire pressure: front 1.8 bar, rear 2 bar (cold). Tire size: front 3.00-21, rear 4.00-18. Always confirm critical values with the workshop manual or an authorised dealer.
OEM and quality aftermarket parts that fit this bike. Always confirm with your dealer before ordering.
Engine oil
Spec: 2-stroke autolube (JASO FC), separate mix-oil reservoir
- OEM OEM 2-stroke oil (JASO FC/FD)
- Premium Motul 710 2T (100% Synthetic)
- Premium Motul 510 2T Technosynthese (Semi-Synthetic)
- Standard Repsol Moto Sintetico 2T (Synthetic)
- Standard Elf Moto 2 Tech (Semi-Synthetic)
Fully Synthetic vs Semi-Synthetic
| Fully Synthetic | Semi-Synthetic | |
|---|---|---|
| Base oil | 100% chemical synthesis (ester or PAO) | Mineral oil + synthetic additives |
| Heat resistance | Excellent — stable at extreme heat & RPM | Good — suitable for normal temperatures |
| Cold start | Better — reaches engine faster when cold | Good — adequate for normal climates |
| Change interval | Longer (up to 10,000 km) | Shorter (5,000–7,000 km typical) |
| Price | Higher | Lower |
Oil filter
Spec: Not applicable — 2-stroke engine has no replaceable oil filter cartridge
- OEM 2-stroke engine — no engine-oil filter to replace.
- OEM Use the recommended 2-stroke oil grade listed above — clean oil is your only filtration.
Air filter
Spark plug
Spec: NGK B8ES, gap 0.8 mm
- OEM NGK B8ES
- Premium NGK BR8EIX
- Standard NGK B8ES
Front brake pads
Rear brake pads
Drive chain
Spec: 102 links | Sprockets 17/42 teeth / 102 links
Front tire
Spec: 3.00-21, 1.8 bar
- OEM OEM 3.00-21
Rear tire
Spec: 4.00-18, 2.0 bar
- OEM OEM 4.00-18
Battery
- Premium Yuasa YTX9-BS or YTZ7S (typical 250-500cc)
Brake fluid
- Standard TotalEnergies HBF4
Coolant
Service interval
Spec: 3 000 km / 12 months
- OEM Engine oil + oil filter change
- OEM Air filter inspection
- OEM Spark plug check
- OEM Brake fluid replacement: every 2 years
Valve check
Spec: Not applicable — 2-stroke engine has no valves
- OEM 2-stroke engine — no valve clearance to inspect.
- OEM Inspect piston, rings and cylinder at engine rebuild intervals (~30–50 hours for race, longer for street).
- OEM Check exhaust power-valve operation (if equipped) every 20–30 service hours.
