Yanmar 4BY - Adjusting Camshaft Timing

ENGINE
BY Service Manual
5-49
Camshaft and Timing Gear Train
Adjusting Camshaft Timing
Figure 5-73
1. Rotate the crankshaft until No. 1 cylinder intake
camshaft lobes are facing down.
IMPORTANT
Do not remove the camshaft sprocket bolts.
Note: One bolt must be loosened prior to
rotating No. 1 piston to TDC position.
2. Loosen one bolt (Figure 5-73, (1)).
Figure 5-74
3. Rotate the crankshaft in the normal running
direction until No. 1 cylinder is at TDC of the
power stroke. The front lobe of each camshaft
(Figure 5-74, (1)) will be facing toward the
exhaust side and the timing marks
(Figure 5-74, (2)) will meet.
4. Verify position by checking the camshaft timing
marks (Figure 5-74, (2)) on gears are aligned.
The single mark on intake camshaft gear must
fall between the two marks on the exhaust
camshaft gear.
Figure 5-75
IMPORTANT
DO NOT rotate the crankshaft backward. If
the crankshaft is turned past TDC, rotate
two more turns (720°) to bring No. 1 piston
back to TDC.
5. Secure crankshaft in TDC position with flywheel
holding tool (Figure 5-71).
Figure 5-76
6. Loosen two remaining bolts (Figure 5-76, (1)).
0003774
(1)
0003771
(
2
)
(
1
)
0003775
(
1
)