Yanmar 2YM15 Service Manual download pdf (Page 152)

5. Inspection and servicing of basic engine parts

132

5.8 Flywheel and housing

The function of the flywheel is through inertia, to rotate the crankshaft in a uniform and smooth manner

by absorbing the turning force created during the combustion stroke of the engine, and by compensating

for the decrease in turning force during the other strokes.

The flywheel is mounted and secured by 6 bolts on the crankshaft end at the opposite end to the gear

case; it is covered by the mounting flange (flywheel housing) which is bolted to the cylinder block.

The fitting surface for the damper disc is on the crankshaft side of the flywheel. The rotation of the

crankshaft is transmitted through this disc to the input shaft of the reduction and reversing gear. The

reduction and reversing gear is fitted to the mounting flange.

The flywheel’s unbalanced force on the shaft center must be kept below the specified value for the

crankshaft as the flywheel rotates with the crankshaft at high speed.

To achieve this, the valance is adjusted by drilling holes in the side of the flywheel, and the unbalanced

momentum is adjusted by drilling holes in the circumference.

The ring gear is shrink fitted onto the circumference of the flywheel, and this ring gear serves to start the

engine by meshing with the starter motor pinion.

The stamped letter and line which show top dead center of each cylinder are positioned on the flywheel

circumference, and by matching these marks with the arrow mark at the hole of the flywheel housing, the

rotary position of the crankshaft can be ascertained in order to adjust tappet clearance or fuel injection

timing.

5.8.1 Position of top dead center and fuel injection timing

(1) Marking

(2) Matching mark

The matching mark is made at the hole of the flywheel

housing.

Hole

Flywheel

housing

Injection

timing marks

Flywheel

T.D.C.

No.1 cylinder

Matching mark

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Yanmar 2YM15 Service Manual Page 152