If the seal is being fitted to original equipment you may have some influence over the shaft and housing bore finish, but if you are replacing a worn seal you still need to take into account the condition of these 2 essential parts.
Cover the valve gear with a clean cloth to prevent dirt getting into the working parts of the engine.
For more detailed information, please see the following:

black spark plug. This increased durability can result in fewer maintenance issues and a more reliable engine overall.
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Oil seals are always exposed to a lot of chemicals, both mild and harsh chemicals. The seals react by showing some signs like cracks, blisters, and discoloration especially when the chemical is harsh. This clearly shows that the chemical is not compatible with the seal, which goes as far as affecting its cross-link density (increase or decrease). When the cross-link density increases, the seal material becomes harder, but when it decreases, the seal material becomes softer.
There are several key factors to consider when you are selecting the oil seals for your next project to ensure that you protect your machinery from immediate and long-term damage.
As shown in Figure 1, sealing devices come in two types: contact and non-contact.
Oil seals are among the major contact type sealing devices.



Seals are classified by O.D. wall material, lip type, and whether they have a spring or not.
Major oil seals are specified in ISO 6194-1 and JIS B 2402-1.
Table 2 shows the common types of oil seals, while Table 3 shows the features of each type of oil seal.
Table 4 lists the JTEKT oil seal type codes and corresponding ISO and JIS standards.
In addition to carbon buildup and oil leakage, black spark plugs can also be caused by overheating. If the engine is running too hot, it can cause the electrodes on the spark plugs to wear down and become coated in carbon deposits. This can lead to poor engine performance and reduced fuel efficiency. It is important to monitor the engine temperature and address any overheating issues promptly to prevent damage to the spark plugs.
One way to recognize an improperly installed seal is by checking whether or not there is uneven shearing of the rubber after use. If this is evident, adjust by aligning the installation tools properly before pressing the seal into place.
Please see the following for the types of sealing devices for bearings.
How to Select the Right Bearing (Part 7): Components surrounding the bearing