Precautions for crankshaft installation

As the core transmission component of the engine, the installation accuracy of the crankshaft directly determines the operational stability and service life of the engine. The installation process must strictly follow the process specifications, control every detail, and avoid faults such as journal wear, engine shaking, and even crankshaft fracture caused by improper installation. The following are the core precautions for crankshaft installation, covering the entire process before, during, and after installation.

1、 Before installation: Clean and inspect the components properly

Before installation, it is necessary to thoroughly clean the core components such as the crankshaft, cylinder block, main bearing pad, and main bearing pad, removing surface oil stains, metal debris, rust inhibitors, and other impurities to prevent impurities from entering the friction surface and causing later wear. Simultaneously complete key inspections: check whether the roundness and cylindricity of the crankshaft journal meet the standards, and whether there are any tensile marks or cracks on the surface; Check the coaxiality of the main shaft bearing of the cylinder body. If there is any deformation, it needs to be repaired first; Check the thickness specifications of the main bearing tile to ensure compatibility with the crankshaft journal. The new tile needs to be inspected for surface damage and alloy layer detachment. In addition, it is necessary to prepare auxiliary materials such as seals and lubricating grease that meet the requirements of the original factory.

2、 During installation: Control assembly accuracy and operating standards

The assembly process is the core of crankshaft installation, and the first priority is to install the main bearing shell. The upper and lower bearings should be distinguished according to the cylinder body markings, and sealant should be evenly applied to the back of the bearing shell (to fit the sealing surface without overflow). Engine specific assembly grease should be applied to the surface of the bearing shell to avoid dry grinding. When installing the crankshaft, handle it gently and slowly insert it into the main shaft bearing seat to prevent collision with the shaft neck and bearing surface; Tighten the main shaft bearing cover bolts in the order and torque specified by the original factory, using the "cross tightening in stages" method. Increase the torque to the standard value in 2-3 stages to avoid deformation of the cylinder body and excessive coaxiality caused by tightening a single bolt at once. At the same time, check the rotational flexibility of the crankshaft. When rotating the crankshaft by hand, it should be smooth without any jamming or abnormal resistance. If the rotation is too tight, it should be disassembled and checked immediately. Do not forcefully rotate it.

3、 After installation: perform re inspection and initial lubrication

After the crankshaft assembly is completed, multiple re inspections are required: use a dial gauge to check the axial and radial clearances of the crankshaft to ensure that they are within the original factory standard range. If the clearance is too large, it can easily cause the crankshaft to move, and if it is too small, it can affect lubrication; Recheck the tightening status of all bolts to prevent missing or insufficient torque. After installation, add engine oil that meets the specified label. First, manually rotate the crankshaft several times to fully lubricate the friction surface between the main journal and the bearing shell with the engine oil; After starting the engine, keep it idling and avoid running at high speeds and high loads in the initial stage. Observe whether there is any abnormal noise from the engine and whether the oil pressure is normal. After confirming that there are no abnormalities, proceed with subsequent component assembly and testing.

The core of crankshaft installation lies in "precision" and "standardization", and any negligence in detail may lead to subsequent engine failures. Strictly following the above precautions is necessary to ensure the assembly accuracy of the crankshaft and lay the foundation for the stable operation of the engine.