1. Adjustment of valve foot space: valve arrangement in normal operation, with the wear of parts, the valve foot space will change. If the cam, valve rod end face and tappet contact surface wear, the open space will become larger, while the valve head and valve seat wear, the open space will become smaller. Therefore, the base value of open space should be taken in the adjustment. If the rule is 0.2 ~ 0.25 mm, the actual value can be 0.22 mm. This not only takes into account the actual situation of the change of the open space, but also considers the question of the measurement error, which can fully ensure the completion of the air gap effect of the valve foot.
2. Valve seat reaming: valve seat reaming is usually a manual operation, and three questions should be paid special attention to: first, on the basis of eliminating depression and mottling, and reaming out no missing cone surface, the smaller the reaming amount is, the better; second, the force should be even when reaming, and the knife should be lifted and closed lightly, and more investigation should be carried out to ensure less reaming amount and higher smoothness; The third is to match with the valve to determine the working face orientation and width. The orientation should be adjusted to the middle and lower part of the valve cone surface, and the upper and lower reamers can be used to adjust the position. The width of working face can be controlled within 0.9mm for inlet valve and 1.4mm for exhaust valve (1.5-2.5mm). Practice has proved that after grinding the valve and valve seat, the inlet valve can reach 1 mm and the exhaust valve can reach 1.5 mm, which are both within the lower limit of the regular width, which can greatly improve the service life of the valve.
3. The repair quality of mixer truck is poor. In the repair operation, the outstanding question is that the processing quality of valve and valve seat working surface can not meet the requirements, which constitutes ablation and depression of working surface, and early damage; camshaft bearing in scraping, its cooperation space, contact area, bearing concentricity can not meet the requirements, accelerate wear and appear abnormal noise, which constitutes early damage; when valve guide is replaced with new parts, hinge Cutting quality can not meet the requirements, which directly affects the service life of valve and valve seat.
4. Scraping of camshaft bearing: scraping of camshaft bearing belongs to manual operation, so it is difficult to ensure quality. For the convenience of scraping, it is usually processed outside the cylinder. Therefore, we should pay special attention to the following four questions: first, determine the diameter of the inner hole of the bearing after scraping; second, pay attention to the coaxiality between the inner hole and the outer circle of the bearing; third, try to fit the bearing with the journal while scraping, and ensure that the contact marks are evenly distributed; fourth, when pressing the bearing into the seat hole, pay attention to aligning the oil hole. After scraping, install the camshaft, roll it for several turns, and properly trim it according to the situation. The contact area should reach more than 75% and be evenly distributed. The open space should meet the regulations.