XU series engine
1. On early models of engines, when overhauling, it is necessary to install new liners. On later engine models, running clearance can be checked using the original bushings. However, it is preferable to use a new set, as the results obtained will be more accurate.
2. Clean the back of the bushing and its mounting location in the cylinder block and main bearing caps.
3. Install the earbuds in place. Note that the upper bearing shells have a grooved running surface while the lower bearing shell has a solid running surface.
4. The working clearance can be checked in two ways.
5. One of the methods (which assumes the presence of a micrometer to measure the diameter of the holes) consists in installing the main bearing caps together with the liner on the cylinder block and screwing them to the required torque. Measure the inside diameter of each assembled pair of bearing shells. Measure the diameter of each crankshaft main journal. Subtract the corresponding crankshaft journal diameter from the measured bearing diameter.
6. Second (and more accurate) the method is to use a product known as Plastigage. This is a round plastic rod that is compressed between the liner and the crankshaft journal. After removing the main bearing cap, the deformed plastic rod is measured with a special gauge, which is included in the Plastigage kit. The procedure for using Plastigage is as follows.
7. On the liners installed in the engine block, install the crankshaft without lubrication. The crankshaft journals and bearings must be completely clean and dry.
8. Cut off a few pieces of the plastic Plastigage rod (they should be slightly shorter than the width of the main bearings) and install them on each crankshaft journal.
9. Install the covers with the bottom liners and tighten the mounting bolts to the required torque. Do not rotate the crankshaft while measuring the clearance using the Plastigage method.
10. Unscrew the cover of the insert attachment, remove it and attach the scale ruler printed on the package to the deformed plastic rod. By comparing the width of the deformed plastic rod with the reference width on the scale bar, determine the amount of gap.
11. Finally, thoroughly clean any traces of Plastigage material from the liners and crankshaft.