Removing the sprocket and timing chain
1. Remove the pistons or, alternatively, disconnect the main bearings if no work is required on the pistons and cylinders. Also remove the camshaft(s) gears, the front crankshaft seal and the flywheel (leading disk).
2. Remove the intermediate disk bolts from the rear of the cylinder block.
3. Release the chain from the front crankshaft sprocket and remove the sprocket by prying it off with a lever. Remove the chain.
4. If necessary, remove the camshaft bracket bolts from the front of the cylinder block and remove the safety (reduction) lubrication system valve. Also, if necessary, remove the lower chain guide.
5. Check the presence of marks on the main bearing caps and, if necessary, make new marks.
6. Before removing the crankshaft, make sure that its axial clearance is within the specified limits. To do this, insert a feeler gauge plate between the crankshaft cheek and the thrust surface of the 2nd bearing shell
7. Loosen the bolts and, lightly tapping on the main bearing caps, remove them together with the bearing shells.
8. Remove the crankshaft upwards from the crankcase.
9. Remove the bearing shells from the covers and the crankcase, marking their relative positions. Also remove (using a lever) the upper half of the rear crankshaft oil seal from the crankcase.