The 1973-1991 Yamaha YB100 Singles repair manual by Haynes, covers motorcycle models indicated.
Book Excerpt: 1973-1991 Yamaha YB100 Singles Repair Manual
ENGINE, CLUTCH AND TRANSMISSION
TRANSMISSION COMPONENTS: REMOVAL
FRAME AND FORKS
- Release the screws which secure the white plastic housing at the end of the transmission selector drum. The housing can be lifted away, and the C-shaped retainer displaced to free the selector drum end. Unscrew the neutral switch assembly from the casing.
The transmission components can be removed as an assembly together with the selector drum and forks, and need not be disturbed unless specific attention is required. Place the assembly to one side.
- The crankcase assembly can be lifted out of the casing, and does not normally require much effort to free it from its bearing.
If necessary, the protruding end of the crankshaft can be tapped with a soft-faced mallet to aid removal, but on no account should heavy blows be applied here, as it is possible to distort the crankshaft if excessive force is used.
EXAMINATION AND REMOVAL: GENERAL
- Before examining the component parts of the dismantled engine/transmission unit for wear, it is essential that they should be cleaned thoroughly. Use a paraffin/gasoline mix to remove all traces of oil and sludge which may have accumulated within the engine.
- Examine the crankcase castings for cracks or other signs of damage. If a crack is discovered, it will require professional attention, or in an extreme case, replacement of the casting.
- Examine carefully each part to determine the extent of wear. If in doubt, check with the tolerance figures whenever they are quoted in the text. The following sections will indicate what type of wear can be expected and, in many cases, the acceptable limits.
- Use clean, lint-free rags for cleaning and drying the various components, otherwise there is a risk of small particles obstructing the internal oilways.
FRONT FORKS: EXAMINATION AND RENOVATION
- The parts most liable to wear over an extended period of time are the bushings and the oil seals, especially where gaiters are not fitted.
Wear is normally accompanied by a tendency for the forks to shudder when the front brake is applied and it should be possible to detect the increased amount of play by pulling and pushing on the handlebars when the front brake is applied fully.
This type of wear should not be confused with slack steering head bearings, which can give identical results.
- Replacement of the worn parts is quite straightforward. Particular care is necessary when replacing oil seals. Both the seal and the fork tube should be greased, to lessen the risk of damage.
- After an extended period of service the fork springs may need a complete set. If the overall length has decreased it is wise to fit new components. Always fit new springs as a matched pair, never separately.
- Check the outer surface of the fork stanchions for scratches or roughness. It is only too easy to damage the oil seals during reassembly, if these high spots are not eased down.
The fork stanchions are unlikely to bend unless the machine is damaged in an accident. Any significant bend will be detected by eye, but if there is any doubt about straightness, roll the stanchions on a flat surface.
If they are bent they must be replaced. Unless specialized repair equipment is available, it is rarely practicable to straighten them to the necessary standard.
- The dust seals must be in good order if they are to fulfill their proper functions. Replace any that are split or damaged.
Subject: 1973, 1974, 1975, 1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991 Yamaha YB100 Singles service, maintenance, repair. ISBN-10: 1850108412 | ISBN-13: 9781850108412 | Haynes 474