Upper Crankcase Reassembly

Upper Crankcase Reassembly xjcdadmin Thu, 04/23/2009 - 15:15


A. Important Information

1.    Gasket and seal

All gaskets and seals should be replaced when an engine is overhauled. All gasket surfaces and oil seal lips must be cleaned.

2.    Properly oil all mating engine and transmission parts and bearings during reassembly.

3.    Circlip

All circlips should be inspected carefully before reassembly. Always replace piston pin clips after one use. Replace distorted circlips.

When installing a circlip, make sure that the sharp edged corner is positioned opposit to the thrust it receives. See the sectional view below.

4. Lock washer/plate and cotter pin

All lock washers/plates and cotter pins must be replaced when they are removed. Lock washer/plate tab(s) should be bent over along the bolt or nut flat(s) after tightening the bolt or nut properly (see illustration).

Cotter pins should be replaced after one use.

B. Engine Assembly 1. Upper crankcase

a. Install the connecting rods onto the crankshaft with the proper connecting rod bearings and apply molybedenum disulfide grease to the bolt threads. Apply torque evenly to both ends of the cap.


While tightening, if a torque of 2.0 m-kg (14.5 ft-lb) or more is reached, DO NOT STOP tightening until final torque is reached.

If tightening is interrupted between 2.0 m-kg and 2.5 m-kg, loosen the nut to less than 2.0 m-kg and start again. Tighten to full torque specification without pausing.

Rod cap torque: 2.5 m-kg (18.1 ft-lb)

b- Install the proper cankshaft main bearings into the crankcase and place the crankshaft. Oil the bearings liberaly.


Do not forget to install the crankshaft oil seal (L.H.), blind plug (R.H.), "HY-VO" chain and cam chain on the crankshaft before installing. Also, install the chain guide into upper crankcase if removed.

c. Install the starter idle gear, shaft, stopper plate, and new lock plate. Tighten the bolt securely and bend the lock tabs along the bolt flats.

1. Lock washer

Tightening torque: 1.0 m-kg (7.2 ft-lb)

d.  Put the starter clutch and sprocket assembly in the "HY-VO" chain and lay it into the crankcase.

e.   Install the A.C.G. Generator shaft into the starter clutch assembly.

f. Install the "HY-VO" chain oil spray nozzle. The locating pin on the nozzle should be placed into the crankcase locating slot. Do not forget to install the new "O-ring" onto the nozzle.

1. O-ring

g. Install the new "O-ring" onto the bearing housing and install it with the panhead screw.

h. Install the transmission main axle assembly on the upper crankcase. Point the bearing locating pin toward the crankshaft and lav it on the case.

1. Bearing locating pin

i. Install the middle driven gear (without the middle drive pinion gear).

j. Install the middle driven gear shaft end bearing.

k. Install the dowel pin with "O-ring" into the crankcase.