Oil clearance check

27.13b... locating the tab in the notch (arrowed)

11 Whether new bearing shells are being fitted or the original ones are being re-used, the main bearing oil clearance should be checked before the engine is reassembled. Main bearing oil clearance is measured with a product known as Plastigauge.

12 Clean the backs of the bearing shells and the bearing housings in both crankcase halves.

13 Press the bearing shells into their cut­outs, ensuring that the tab on each shell engages in the notch in the crankcase (see illustrations). Make sure the bearings are fitted in the correct locations and take care not to touch any shell's bearing surface with your fingers.

14 Ensure the shells and crankshaft are clean and dry. Lay the crankshaft in position in the upper crankcase (see illustration 27.3).

15 Cut several lengths of the appropriate size Plastigauge (they should be slightly shorter than the width of the crankshaft journals). Place a strand of Plastigauge on each

2»48 Engine, clutch and transmission

27.15 Lay a strip of Plastigauge on each journal parallel to the crankshaft centreline

(cleaned) journal (see illustration). Make sure the crankshaft is not rotated.

27.23 Generously lubricate all the bearing shells

16 Carefully install the lower crankcase half on to the upper half (see illustration 21.9). Check that the lower crankcase half is correctly seated. Note: Do not tighten the crankcase bolts if the casing is not correctly seated. Clean the threads of the twelve 8 mm lower crankcase (crankshaft journal) bolts and insert them with their washers in their original locations (see illustration 21.4a or b). Secure all bolts finger-tight at first, then tighten them evenly and a little at a time in the correct numerical sequence to the torque setting specified at the beginning of the Chapter. Make sure that the crankshaft is not rotated as the bolts are tightened.

17 Slacken each bolt evenly a little at a time in a reverse of the numerical sequence until they are all finger-tight, then remove the bolts and washers. Carefully lift off the lower crankcase half, making sure the Plastigauge is not disturbed.

18 Compare the width of the crushed Plastigauge on each crankshaft journal to the scale printed on the Plastigauge envelope to obtain the main bearing oil clearance (see illustration). Compare the reading to the specifications at the beginning of the Chapter.

19 On completion carefully scrape away all traces of the Plastigauge material from the crankshaft journal and bearing shells; use a fingernail or other object which is unlikely to score them.

20 If the oil clearance falls into the specified

27.18 Measure the width of the crushed Plastigauge

range, no bearing shell renewal is required (provided they are in good condition). If the clearance is beyond the service limit, refer to the marks on the case and the marks on the crankshaft and select new bearing shells (see Steps 9 and 10). Install the new shells and check the oil clearance once again (the new shells may bring bearing clearance within the specified range). Always renew all of the shells at the same time.

21 If the clearance is still greater than the
service limit listed in this Chapter's
Specifications (even with new shells), the
crankshaft journal is worn and the crankshaft
should be renewed. Measure the diameter of
each journal and compare the measurements
to the table above to confirm.

Installation

22 Clean the backs of the bearing shells and the bearing cut-outs in both crankcase halves. If new shells are being fitted, ensure that all traces of the protective grease are cleaned off using paraffin (kerosene). Wipe dry the shells and crankcase halves with a lint-free Cloth. Make sure all the oil passages and holes are clear, and blow them through with compressed air if it is available.

23 Press the bearing shells into their cut­outs, ensuring that the tab on each shell engages in the notch In the crankcase (see illustrations 27.13a and b). Make sure the bearings are fitted in the correct locations and take care not to touch any shell's bearing

28.3 Lift the input shaft (A) and the output

shaft (B) out of the crankcase, noting how

the retainer ring (C) and oil seal lip (D)

locate in the grooves

surface with your fingers. Lubricate each shell with molybdenum disulphide oil (a 50/50 mixture of molybdenum disulphide grease and clean engine oil) (see illustration).

24 Lower the crankshaft into position in the upper crankcase, making sure all bearings remain in place (see illustration 27.3). If the cylinder head was not removed, make sure the teeth of the drive gear on the crankshaft mesh with those on the camshaft drive gear assembly.

25 Fit the connecting rods onto the crankshaft (see Section 24).

26 Reassemble the crankcase halves (see Section 21).

I

28 Transmission shafts and bearings - removal and installation

Note: To remove the transmission shafts the engine must be removed from the frame. If the engine has already been removed, ignore the steps which do not apply.

Removal

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

2 On J and К models, lift the output shaft out of the casing, noting how it meshes with the Input shaft. If it is stuck, use a soft-faced hammer and gently tap on the end of the shaft to free it. Remove the bearing half-ring retainer from the left-hand end of the output shaft; if it's not in its slot in the crankcase, remove it from the bearing on the shaft. Grasp the end of the shaft and draw it out of the crankcase. If the needle bearing on the left-hand end of the shaft does not come away with the shaft, remove It from Its cage in the crankcase if required. If required, unscrew the bolt securing the cage retainer in the bore in the crankcase, then remove the retainer and draw out the cage. I-' necessary, the input shaft and output shaft can be disassembled and inspected for v/ear or damage (see Section 29).

3 On L, N and R models, lift the input shaft and output shaft out of the casing, noting how they mesh together (see illustration). If they are stuck, use a soft-faced hammer and gently tap on the encs of the shafts to free them. Remove the dowel for the needle bearing on the left-hand end of the input shaft from the crankcase if it is loose, noting how it fits (see illustrations 28.6a). If it is not in its hole in the crankcase, remove it from the bearing on the shaft. If necessary, the input shaft and output shaft can be disassembled and inspected for v/ear or damage (see Section 29).

4 Referring to Tools and Workshop Tips (Section 5) in the Reference Section, check the bearings. Renew the bearings if necessary, noting that the input shaft right-hand bearing and the output shaft left-hand

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