About the Yamaha RD400
Engine sealing and the later fork changes are key parts decisions on an RD400 restoration.
Yamaha’s RD400 is an air-cooled two-stroke road twin. The U.S.-market 1979 RD400F Daytona Special brought changes to the cylinder head, carburetor controls, forks and brakes. Its 35 mm fork tubes differ from the earlier 34 mm arrangement, making the fitted front end a useful starting point for identification.
Separate the engine repair from the chassis year split
The engine gasket set below lists RD400 1976–1980, but the featured engine oil-seal kit lists 1976–1978. Fork seals also divide into early and later applications. Keep the individual product’s years with the job, especially on an imported bike or one with replacement forks.
Model and year comparisonRD400 parts differences
| Part | Years listed | Selection detail |
|---|---|---|
| Fork oil seals | 1976–1978 | 27-1016: 34 × 46 × 10.5 mm |
| Fork oil seals | 1979–1980 | 27-1007: 35 mm fork application |
| Engine oil-seal kit | 1976–1978 | 01-9022 engine oil-seal kit |
| Engine gasket set | 1976–1980 | 18-0238 engine gasket set |
Prepare for the repairIdentify your RD400 components
Early front end or later RD400F equipment
The U.S. 1979 F changed from 34 mm to 35 mm fork tubes and also changed the calipers and mounts. Match the fitted fork and brake parts separately; the table’s later catalog range is not a claim that all markets used identical equipment.
Gasket joint or oil-seal location
A gasket seals between mating engine surfaces. An oil seal works around its specified shaft or housing location. Identify the leaking location before choosing a set, and compare the exact contents when the engine is already apart.
Contact PartsNMore with your model, year and clear photos of the part and its markings.