Fourth, look for rust on the surface of the parts. The surface of qualified parts has both a certain degree of accuracy and a bright finish. The more important the parts, the higher the precision, and the stricter the rust and corrosion protection of the packaging. Should pay attention to check when purchasing, if you find that the parts have rust spots, mildew spots, or rubber parts are cracked, lose elasticity, or the surface of the journal has obvious turning tool lines, they should be replaced.
Fifth, see if the protective surface is intact. Most parts are coated at the factory. For example, piston pins and bushes are protected with paraffin; piston rings and cylinder liners are coated with rust-proof oil and wrapped with wrapping paper; valves, pistons, etc. are dipped in rust-proof oil and sealed in plastic bags. If you find that the sealing sleeve is damaged, the packaging paper is lost, or the anti-rust oil or paraffin is lost during the purchase, it should be returned.
6. See if the glued parts are loose. An accessory composed of two or more parts. The parts are press-fitted, glued or welded. There must be no looseness between them. For example, the oil pump plunger and the adjusting arm are combined by press-fitting. The clutch driven wheel and the steel plate are riveted, the friction plate and the steel plate are riveted or glued; the frame of the paper filter element is glued to the filter paper; the wire ends of the electrical equipment are welded. If looseness is found during the purchase, it should be replaced.
Seven, see if the rotating parts are flexible. When purchasing rotating parts such as oil pumps, you should feel the flexibility and no stagnation when you rotate the pump shaft by hand. When purchasing rolling bearings, support the inner ring of the bearing with one hand, and turn the outer ring with the other hand. Gradually stall. If the rotating parts fail to rotate, it means the internal is rusted or deformed. Do not buy.
Eight, see if there are missing parts in the assembly. The formal assembly components must be complete and intact to ensure smooth assembly and normal operation. If individual small parts on some assembly parts are missed, the assembly parts will not work or even be scrapped.