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Typical bearing failures

• Ball and roller bearings will fail due to lack of lubrication or damage to the balls or rollers. Tapered-roller bearings can be damaged by overloading them. Unless the bearing is sealed on both sides, wash it in paraffin (kerosene) to remove all old grease then allow it to dry. Make a visual inspection looking to dented balls or rollers, damaged cages and worn or pitted races (see illustration 5.18).

• A ball bearing can be checked for wear by listening to it when spun. Apply a film of light oil to the bearing and hold it close to the ear - hold the outer race with one hand and spin the inner


Hold outer race and listen to inner race when spun

race with the other hand (see illustration 5.19).The bearing should be almost silent when spun; if it grates or rattles it is worn.

Oil seals

Oil seal removal and installation

• Oil seals should be renewed every time a component is dismantled. This is because the seal lips will become set to the sealing surface and will not necessarily reseal.

• Oil seals can be prised out of position using a large flat-bladed screwdriver (see illustration 6.1).In the case of crankcase seals, check first that the seal is not lipped on the inside, preventing its removal with the crankcases joined.

6.1Prise out oilseals with a large flat-bladed screwdriver

• New seals are usually installed with their marked face (containing the seal reference code) outwards and the spring side towards the fluid being retained. In certain cases, such as atwo-stroke engine crankshaft seal, a double lipped seal may be used due to there being fluid or gas on each side of the joint.


Tools and Workshop Tips ref.iz


• Use a bearing driver or socket which
bears only on the outer hard edge of the seal
to install it in the casing - tapping on the inner
edge will damage the sealing lip.

Oil seal types and markings

• Oil seals are usually of the single-lipped type. Double-lipped seals are found where a liquid or gas is on both sides of the joint.

• Oil seals can harden and lose their sealing ability if the motorcycle has been in storage for a long period - renewal is the only solution.

• Oilseal manufacturers also conform to the ISO markings for seal size - these are moulded into the outer face of the seal (see illustration 6.2).

These oil seal markings indicate

Inside diameter, outside diameter

And seal thickness

7 Gaskets and sealants

Types of gasket and sealant

• Gaskets are used to seal the mating surfaces between components and keep lubricants, fluids, vacuum or pressure contained within the assembly. Aluminium gaskets are sometimes found at the cylinder joints, but most gaskets are paper-based. If the mating surfaces of the components being joined are undamaged the gasket can be installed dry, although a dab of sealant or grease will be useful to hold it in place during assembly.

• RTV (Room Temperature Vulcanising) silicone rubber sealants cure when exposed to moisture in the atmosphere. These sealants are good at filling pits or irregular gasket faces, but will tend to be forced out of the joint under very high torque. They can be used to replace a paper gasket, but first make sure that the width of the paper gasket is not essential to the shimming of internal components. RTV sealants should not be used on components containing petrol (gasoline).



• Non-hardening, semi-hardening and hard setting liquid gasket compounds can be used with a gasket or between a metal-to-metal joint. Select the sealant to suit the application: universal non-hardening sealant can be used on virtually all joints; semi-hardening on joint faces which are rough or damaged; hard setting sealant on joints which require a permanent bond and are subjected to high temperature and pressure. Note:Check first if the paper gasket has a bead of sealant


impregnated in its surface before applying additional sealant.

• When choosing a sealant, make sure it is suitable for the application, particularly if being applied in a high-temperature area or in the vicinity of fuel. Certain manufacturers produce sealants in either clear, silver or black colours to match the finish of the engine. This has a particular application on motorcycles where much of the engine is exposed.

• Do not over-apply sealant. That which is squeezed out on the outside of the joint can be wiped off, whereas an excess of sealant on the inside can break off and clog oilways.

Breaking a sealed joint

• Age, heat, pressure and the use of hard setting sealant can cause two components to stick together so tightly that they are difficult to separate using finger pressure alone. Do not resort to using levers unless there is a pry point provided for this purpose (see illustration 7.1)or else the gasket surfaces will be damaged.

• Use a soft-faced hammer (see illus­tration 7.2)or a wood block and conventional hammer to strike the component near the mating surface. Avoid hammering against cast extremities since they may break off. If this method fails, try using a wood wedge between the two components.

7.1 If a pry point is provided, apply gently pressure with a flat-bladed screwdriver


| Caution: If the joint will not separate, double-check that you have removed all I the fasteners.

7.2 Tap around the joint with a soft-faced mallet if necessary - don't strike cooling fins

Removal of

old gasket and sealant

• Paper gaskets will most likely come away complete, leaving only a few traces stuck on


Most components have one or two hollow locating dowels between the two gasket faces. If a dowel cannot be removed, do not resort to gripping it with pliers - it will almost certainly be distorted. Install a close-fitting socket or Phillips screwdriver into the dowel and then grip the outer edge of the dowel to free it.

the sealing faces of the components. It is imperative that all traces are removed to ensure correct sealing of the new gasket. • Very carefully scrape all traces of gasket away making sure that the sealing surfaces are not gouged or scored by the scraper (see illustrations 7.3, 7.4 and 7.5).Stubborn deposits can be removed by spraying with an aerosol gasket remover. Final preparation of


7.5 ... or a household scraper


Date: 2016-01-14; view: 213


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