One of the main causes of black spark plugs is a rich air-fuel mixture. This means that there is an excess of fuel in the combustion chamber, which can lead to incomplete combustion and the production of carbon deposits. A rich air-fuel mixture can be caused by a variety of factors, including a faulty oxygen sensor, a clogged air filter, or a malfunctioning fuel injector. It is important to address these issues promptly to prevent further damage to the spark plugs and the engine.
black spark plug

If oil is dripping down your motorcycle’s tube, your vehicle’s performance will be affected. It won’t have as much power, and you’ll notice it acting sluggishly.
It is quite common for a groove to develop at the sealing lip at some point due to long-term use. As a result, the new oil seal no longer fits and seals properly. It is not strictly necessary to replace or repair the entire shaft. Take a closer look at the dimensions first. It may be possible to fit with a slightly narrower or wider oil seal next to the groove. Alternatively, using the Speedi-Sleeve repair kit, repair the running surface under the seal.
Installation inaccuracies
1 .Material: There are 7 types of material used for oil seals, they are.