B . and fit the side rails each side of it. The oil ring must be installed by hand

12 Finally, install the top ring in the same manner into the top groove in the piston. Make sure the identification letter near the end gap is facing up.

13 Once the rings are correctly installed, check they move freely without snagging and stagger their end gaps as shown (see illustration).

I

27 Crankshaft and main bearings - removal, inspection and installation

Note: To remove the crankshaft the engine must be removed from the frame and the crankcase halves separated.

Removal

1 Remove the engine from the frame (see Section 5) and separate the crankcase halves (see Section 21).

2 Separate the connecting rods from the crankshaft (see Section 24).

Note: If no work is to be carried out on the piston/connecting rod assemblies there is no need to remove them from the bores. although the connecting rod bearing caps must be removed (see Section 24, Steps 3 and 4 or 5) and the pistons pushed up to the top of the bores so that the connecting rod ends are positioned clear of the crankshaft.

3 Lift the crankshaft out of the upper
crankcase half, taking care not to dislodge the
main bearing shells (see illustration).

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Lift the crankshaft out of the crankcase...

Engine, clutch and transmission 2*47

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And remove the shells if required 27.9a Main bearing journal size numbers

(arrowed)

B Main bearing housing size letters (arrowed)

	Main journal code
Crankcase code	1- (29.993 to 30.000 mm)	2-(29.984 to 29.992 mm)
A- (33,000 to 33.008 mm)	D - Pink	С - Yellow
В-(33.009 to 33.016 mm)	С - Yellow	В - Green
С-(33.017 to 33.024 mm)	В - Green	A - Brown

4 The main bearing shells can be removed
from the crankcase halves by pushing their
centres to the side, then lifting ihem out (see
illustration). Keep the shells in order.

Inspection

5 Clean the crankshaft with solvent, using a rifle-cleaning brush to scrub out the oil passages. If available, blow the crank dry with compressed air, and also blow Ihrough the oil passages. Check the primary drive gear and the camshaft drive gear for wear or damage. If any of the gear teeth are excessively worn, chipped or broken, the crankshaft must be renewed. If wear or damage is found, also check the primary driven gear on the back of the clutch housing (see Section 16) and the camshaft drive gear assembly (see Section 13).

6 Refer to Section 23 and examine the main bearing shells. If they are scored, badly scuffed or appear to have been seized, new bearings must be Installed. Always renew the main bearings as a set. II they are badly damaged, check the corresponding crankshaft journals. Evidence of extreme heat, such as discoloration, indicates that lubrication failure has occurred. Be sure to thoroughly check the oil pump and pressure regulator as well as all oil holes and passages before reassembling the engine.

7 Give the crankshaft journals a close visual examination, paying particular attention where damaged bearings have been discovered. If the journals are scored or pitted in any way a new crankshaft will be required. Note that undersizes are not available, precluding the option of re-grinding the crankshaft.

8 Place the crankshaft on V-blocks and check the runout at the main bearing journals using a dial gauge. Compare the reading to the maximum specified at the beginning of the Chapter. If the runout exceeds the limit, the crankshaft must be renewed.

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