The crankshaft can only be removed after the engine has been taken out of the vehicle and fully disassembled. Ensure that the main bearing caps are marked according to their original locations. Unbolt the main bearing caps while keeping their shell bearings together with the respective caps if they are to be reused. With assistance, lift the crankshaft from the crankcase. If the upper half shell bearings are to be removed for reuse, keep them identified and separate from their corresponding lower half shell bearings. Remove the two halves of the crankshaft rear oil seal. Replacing the main bearings while the engine is still in the vehicle carries some risk due to potential dirt deposits on the bearing shell faces during installation, but some may find the work-saving aspect worthwhile. Begin by removing the engine oil pan, oil pump, and spark plugs. Identify the main bearing caps. To replace the main bearing shells with the crankshaft in position, first loosen each of the main bearing caps without removing them. Remove the No. 1 main bearing cap, extract the shell bearing from the cap, and fit the new one after lubricating it with engine oil. Insert a cotter pin in each of the crankshaft journal oil holes and turn the crankshaft clockwise until the cotter pin head slides the upper shell from its seat in the crankcase. Fit the new upper shell in the same manner, ensuring it is well-oiled and inserting the plain end first. Remove the cotter pin, fit the bearing cap with the 'F' mark facing the front of the engine, and tighten the cap bolts finger-tight. Repeat these operations for the remaining main bearings and then tighten all cap bolts to the specified torque.