11. Dismantling the engine unit: removing the crankcase lower section and the output/balancer shaft
While these components can be removed with the main cylinder block
casting still in the frame, this is not recommended. It will leave the
engine unit supported precariously at its rear end and attached the
frame by two bolts (only one if the cylinder head is removed) and a few
ancillary components; when one realizes that the frame is supported only
by the front wheel and its rear end, the potential for serious damage
and personal injury may be appreciated.
Since the removal of the engine/transmission unit complete involves so
little extra work and affords so much safer working conditions and
improved access, it is the only recommended method of gaining access to
Remove the Allen screws along the left- and right-hand mounting
of the crankcase lower section, then remove the two hexagon-headed bolts
from the inside rear and the two Allen-headed bolts or screws from the
inside front. Tap the lower section with a soft-faced mallet to break
the joint and withdraw the lower section noting the 0-rings around
the oil and coolant passages and the two to locating dowels, one next to
each output shaft bearing. Unless the dowels are firmly fixed in the
crankcase/cylinder block, they should be removed.
On 75 models, slowly rotate the crankshaft and balancer shaft until
timing marks can be seen. These should be in the form of a straight line on the crankshaft gear which aligns with either a dot or a V
mark on the balancer gear. Do not disturb either shaft until the
marks have been found and noted.
Withdraw the output/balancer shaft and its rear seal noting that its front
needle roller bearing is loosely fixed and may drop clear.
On some early models whose output shafts are fitted with rear bearings which have a thin (1.75
mm/0.07 in thick) locating circlip at
the forward end of the bearing outer race, the bearing may be glued in
place with Loctite 273, Three Bond 1110 B or similar adhesive. If any difficulty is encountered in removing such a bearing, the
adhesive should be heated (maximum of 300 °C/572 °F) to break it down and to release the bearing.