General
The crankcase halves must be separated to service the connecting rod, crankshaft and transmission (including the shift fork and shift drum). To service these parts, the engine must be removed from the frame (section 7).
The following parts must be removed before disassembling the crankcase.
- Cylinder head (section 8)
- Cylinder and piston (section 9)
- Clutch, primary drive gear, primary shaft and gearshift linkage (section 10)
- Water pump (section 6)
- Starter motor and starter drive gear (section 18)
- Flywheel and starter clutch (section 18)
Be careful not to damage the crankcase mating surfaces when servicing.
Mark and store the connecting rods and bearings to be sure of their correct locations. If the bearings are improperly installed they will block the oil holes, causing insufficient lubrication and eventual engine seizure.
Be careful not to damage the main journal bearing inserts during crankshaft removal and installation.
Connecting rod bearing inserts are select fitted and are identified by color code. Select replacement bearings from the code table. Check the oil clearance using a plastigauge after replacing bearing inserts.
Prior to assembling the crankcase halves, apply sealant to their mating surfaces. Wipe off excess sealant thoroughly.
Replace the output drive gear and driven gear as a set.
Whenever you replace the out put driven/drive gears, bearings, bearing holder or gear case, perform the gear contact pattern and backlash inspection and adjust the shim. The extension lines from the gear engagement surfaces should intersect at one point.
Protect the output gear case with a shop towel or soft jaws while holding it in vise. Do not clamp it too tightly as it could damage the gear case.
Specification
ITEM | STANDARD | SERVICE LIMIT Unit: mm (in) | ||
Crankshaft | Connecting rod side clearance | 0.10-0.25 (0.004-0.010) | 0.28 (0.011) | |
Crankpin bearing oil clearance | 0.032 - 0.062 (0.0015 - 0.0024) | 0.070 (0.0028) | ||
Main journal bearing oil clearance | 0.030 - 0.054 (0.0011 - 0.0021) | 0.068 (0.0027) | ||
Runout | — | 0.05 (0.002) | ||
Shift fork, fork shaft | I.D. | 14.000 - 14.018 (0.5512 - 0.5519) | 14.04 (0.553) | |
Claw thickness | 5.93 - 6.00 (0.233 - 0.236) | 5.83 (0.230) | ||
Shift fork shaft O.D. | 13.966 - 13.984 (0.5498 - 0.5506) | 13.956 (0.5494) | ||
Transmission | Gear I.D. | M4, M5 | 31.000 - 31.025 (1.2205 - 1.2215) | 31.035 (1.2218) |
C1 | 30.000-30.025 (1.1811 - 1.1821) | 30.035 (1.1825) | ||
C2, C3 | 33.000 - 33.025 (1.2992 - 1.3002) | 33.035 (1.3006) | ||
Gear bushing O.D. | M4,M5 | 30.950 - 30.975 (1.2185 - 1.2195) | 30.94 (1.218) | |
C1 | 25.987 - 26.000 (1.0232 - 1.0236) | 25.977 (1.0227) | ||
C2/C3 | 32.950 - 32.965 (1.2972 - 1.2978) | 32.94 (1.297) | ||
Gear-to-bushing clearance | M4, M5 | 0.025 - 0.075 (0.0010 - 0.0030) | 0.095 (0.0037) | |
C2, C3 | 0.035 - 0.075 (0.0014 - 0.0030) | 0.095 (0.0037) | ||
Gear bushing I.D. | M4 | 27.985 - 28.006 (1.1018 - 1.1025) | 28.03 (1.104) | |
C1 | 22.050 - 22.150 (0.8681 - 0.8720) | 22.170 (0.8728) | ||
C2/C3 | 30.000-30.030 (1.1811 - 1.1823) | 30.050 (1.1831) | ||
Mainshaft O.D. | at M4 | 27.959 - 27.980 (1.1007 - 1.1016) | 27.940 (1.1000) | |
Clutch outer guide | 27.980 - 27.993 (1.1016- 1.1021) | 27.970 (1.1012) | ||
Countershaft O.D. | at C1 | 21.980 - 21.993 (0.8653 - 0.8659) | 21.97 (0.865) | |
at C2/C3 | 29.959 - 29.980 (1.1795 - 1.1803) | 29.94 (1.179) | ||
Bushing-to-shaft clearance | M4 | 0.005 - 0.047 (0.0002 - 0.0019) | 0.067 (0.0026) | |
C1 | 0.057 - 0.170 (0.0022 - 0.0067) | 0.190 (0.0075) | ||
C2/C3 | 0.020 - 0.071 (0.0008 - 0.0028) | 0.091 (0.0036) |
Torque values
Right crankcase bolt | 26 N·m (2.7 kgf·m, 20 lbf·ft) | |
Left crankcase bolt | 26 N·m (2.7 kgf·m, 20 lbf·ft) | |
Left crankcase oil orifice bolt | 14 N·m (1.4 kgf·m, 10 lbf·ft) | |
Connecting rod bearing cap bolt | 49 N·m (5.0 kgf·m, 36 lbf·ft) | Apply oil to the threads and flange surface. |
Output gear case mounting bolt | 31 N·m (3.2 kgf·m, 23 lbf·ft) | |
Output drive gear bearing holder bolt | 31 N·m (3.2 kgf·m, 23 lbf·ft) | |
Output drive gear bearing holder socket bolt | 31 N·m (3.2 kgf·m, 23 lbf·ft) |
Tools
Remover weight | 07936-371020A or 07936-3710200 |
Attachment, 32 x 35 mm | 07746-0010100 |
Attachment, 42 x 47 mm | 07746-0010300 |
Attachment, 52 x 55 mm | 07746-0010400 |
Attachment, 62 x 68 mm | 07746-0010500 |
Pilot, 25 mm | 07746-0040600 |
Pilot, 22 mm | 07746-0041000 |
Pilot, 28 mm | 07746-0041100 |
Driver | 07749-0010000 |
Mainshaft holder | 07923-6890101 |
Remover handle | 07936-3710100 |
Bearing remover | 07936-3710300 |
Bearing remover, 22 mm | 07936-3710600 |