CR AN KS HA FT A ND F LY WH EE L AS SE MB LY
Crankshaft is made of QT900-2 nodular cast iron. Main bearing is made of steel back 20%
alloy with high tin and aluminum which can't adhere oil while mounting to avoid affecting its
radiating efficiency and damaging bearings. The thrust plate is of the same material as main
bearing. They are mounting on two sides of the last main bearing and positioned by the convex tail
of the lower thrust plate. When mounting, the oil channel of thrust plate should face to crankshaft
thrust surface. Reverse mounting is not allowed.
Main bearing cover is machined in couple with cylinder block. Cylinder block No. and
sequence No. are engraved on main bearing cover. The forth-main bearing cover is positioned by
positioning bushing. When mounting, the top arrow on main bearing should back- face to the side
of camshaft and compile the number from front end.
Reverse mounting is not allowed. Tightening torque of main bearing bolts is 115~130N.m. when
tightening, firstly tighten the central one, then the two sides alternatively. After tightened, the
crankshaft should run freely.
Flywheel is positioned by pin and tightened by bolts on the crankshaft rear end. Bolts are
tightened at a torque of 50 - 60 N. m alternatively on diagonal line. The belt pulley is positioned
by starting paw, tightened at a torque of 160-170 N.m on the crankshaft front end. Pounding or
beating is strictly prohibited when mounting or dismounting.
Crankshaft, flywheel and belt pulley, have been balanced. Care must be taken of ensuring its
balance when replacing parts. Both flywheel housing and gear case cover are mounted with oil
seal. Do not damage them when mounting or dismounting.
4 . P IS TO N AN D CO NN E CTI NG RO D ASS E MB LY
The piston is made of aluminum alloy ZL109, which has tow air--compression rings and one
oil scraper ring.
The first compression ring is of chrome- plated barrel shape; the second one is of taper shapes.
The oil scraper ring is spiral spring expanding ring with the inner cylinder face, inner round face
and outer cylinder edge face plated by chrome, pay attention that the spring connecting point
should space out 180° apart from the oil scraper ring gap.
It is advised to install the piston ring with special expander; excessive expanding is not
allowed to avoid breaking. The ring should turn easily in the slot and can fall into the slot
supporting face by itself. The piston concave should be poured lub.oil.
The piston ring shape and its opening direction, please refer to Fig.4 and Fig.5
Fig.4 Piston ring shape Fig.5 Piston ring opening direction
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