ZONGSHEN ZS125-86 Service Manual page 12

in gasoline for a few minutes can make the decomposition easier.
[10.]Washers and gaskets shall be decomposed meticulously in ways to prevent from damages.
2)Cleaning the Parts
Parts having been removed are mostly stained with greasy dirt or carbon deposits. Cleaning such
parts favors the maintenance and fitting. Gasoline, kerosene and cleaning fluid are optional. The cleaning
method is determined according to the characteristics of the part to be cleaned.
[1.]Cleaning greasy dirt
Metal parts can be cleaned by way of cold wash and hot wash. Put the parts are in gasoline or
kerosene as the cleaning agent and scrub with a brush. This is called the cold wash method. In respect
of hot wash method, put parts in alkaline solution as a cleaning agent, heat it to 79℃ ~ 90℃, and then
soak for 10min ~ 15min. After that, take out the parts and rinse.
Nonmetal parts should be cleaned in different methods based on the different materials. Rubber parts
should be cleaned by use of alcohol, and it is strictly prohibited to use kerosene or gasoline, lest the rubber
would swell and go bad. However, the clutch and brake shoes shall be scrubbed with gasoline, instead of
alkaline solution.
[2.]Removing carbon deposits
Carbon deposits on machine elements can be removed in the mechanical method or chemical method.
As for the mechanical method, a bamboo scraper or blade is first applied to remove carbon deposits, and
then purify the element with gasoline; as to the chemical method, a hairbrush is used to remove carbon
deposits after the element has been soaked in a cleaning solution and finally wash it with hot water.
3)Detecting the Parts
Cleaned parts should be rendered for appropriate detection operations. The purpose of detection is
to determine whether a part needs to be repaired or discarded. Parts detection methods include direct
inspection, measurement and probing.
[1.]Direct inspection
Instruments and other tools are not necessary in a direct inspection, which relies solely on the human
sensory organs to test and determine the technical status of parts. Simple and easy to practice, this
method is widely used in maintenance.
[2.]Measurement
The measurement method is to measure dimensions and geometrical shapes of parts with gauges and
instruments and compare the obtained data with the allowable limits to determine the technical condition
of parts. By this method, results are highly accurate, but the precision of measuring instruments and tools
must be carefully checked before the detection, and components to be measured should be reasonably
chosen.
[3.]Probing
Concealed defects on parts can be detection by way of probing. The simplest immersion-based
hammering method is generally applied in the maintenance. In this method, a part to be detected is
firstly immersed into kerosene or diesel for a few minutes. Take it out and dry the surface. Spread talcum
powder evenly on the surface of the part, and then tap gently the part on a non-working surface with a
small hammer. As the hammering will cause a vibration of the part, if the part has a crack, the oil left in
the crack when the part is immersed will be spilled out due to the vibration and make the talcum powder
yellow-colored on the surface, so that a yellow line emerges on the crack.
4)Maintenance Methods and Skills
In the maintenance process, it comes to main maintenance stage after decomposition, cleaning and
detection, etc. Mastering the basic maintenance skills is the key to ensure the quality of maintenance.
Machine elements are generally maintained in the following methods:
[1.]Chiseling, filing, and scraping
Chiseling is a method applied to process metal parts by means of knocking on a chisel with a hammer.
It functions to cut and split. Filing is a method applied to process metal parts by rasping off a layer of metal
on the surface of a machine element with a file. Filing includes coarse filing and fine filing.
The roughness of the surface of the filed machine element mainly depends on the thickness of file
teeth. The cross-sectional shape of the file and the filing movement are determined by the surface shape
required by the machine element. Scraping is a method applied to process metal parts by razing a layer of
metal on the surface of a machine element with a scraper.
As the scraping is a precision work, so scrapping allowance should not be too large, generally about
6
0.005 ~ 0.01 mm every time. Before scraping, the surface of the machine element should be coated with