Yanmar 2YM15 Service Manual download pdf (Page 43)

2. Inspection and adjustment

(5) Adjusting the intake/exhaust valve clearance

Make measurement and adjustment while the engine is cold.

1) Valve clearance measurement

a) Remove the rocker arm cover above cylinder

head.

b) Set the No.1 cylinder in the compression TDC

Turn the crankshaft to bring the piston of the

No.1 cylinder to its compression top dead center

while watching the rocker arm motion, the timing

mark of the flywheel housing and the top mark of

the flywheel.

(Position where both the intake and exhaust

valves are closed.)

(Notes)

• The crankshaft shall be turned clockwise as seen from the gear case side.

• The No.1 cylinder position is on the opposite side of the gear case.

• Since there is a clearance between the rocker arm and valve at the compression top dead center, the

position of TDC can be checked by hand. Also see that the top mark on the flywheel aligns with the

mark on the flywheel housing. If there is no valve clearance, disassemble and inspect around the

valve seat, since the valve seat may be worn abnormally.

c) Valve clearance measurement

Insert a thickness gage between the rocker arm

and valve cap, and record the measured valve

clearance.

(Use it as the data for estimating the wear state.)

d) Adjusting other cylinders

Turn the crankshaft 240

° and make adjustment

for the No.3 cylinder. Then adjust the No.2

cylinder in this order.

The cylinder to be adjusted first does not have to

be the No.1 cylinder. Select and adjust the

cylinder where the piston is the nearest to the top

dead center after turning, and make adjustment for other cylinders in the order of ignition by

turning the crankshaft 240

° each time.

The adjustment method of reducing the flywheel turning numbers (for reference):

Set No.1 cylinder to the compression T.D.C. and adjust the clearance of the z mark of the below

table. Next, turn the flywheel once (the suction/ exhaust valve of No.1 cylinder is in the position of

the overlap T.D.C. at this time), and adjust the clearance of the

{ mark.

Ignition order of 3 cylinder engines: 1

→ 3 → 2

2) Valve clearance inspection and adjustment

a) Loosen adjusting bolts

Loosen the lock nut and adjust the screw. And

check the valve for any inclination of valve cap,

entrance of dirt or wear.

Cylinder No. 1 2 3

Valve Suction Exhaust Suction Exhaust Suction Exhaust

No.1 compression

T.D. C

zzz zThe first time

No.1 overlap T.D.C {{ The second time

Hole

Flywheel

housing

Injection

timing marks

Flywheel

T.D.C.

No.1 cylinder

Valve

clearance

Rocker arm

(Valve clearance)

Adjusting screw

Lock nut

(Normal) (Abnormal)

Valve cap

1 2 ... 38 39 40 41 42 43 44 45 46 47 48 ... 230 231

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Yanmar 2YM15 Service Manual Page 43

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