Yanmar 4BY - Repair Specifications

ENGINE
5-8
BY Service Manual
Specifications
Repair Specifications
Component Remarks Specification
Cylinder Head
Cylinder Head Must Not Be Machined
Valve Guides Are Not Available as Replacement Parts
Standard Valve Guide ID - Intake
6.0 +0.015 mm
(0.2362 +0.0006 in.)
Standard Valve Guide ID - Exhaust
6.0 +0.015 / +0.03 mm
(0.2362 +0.0006 / +0.0012 in.)
Valve Side Movement (Max.) (Valve-to-Guide Wear)
0.5 mm
(0.020 in.)
Camshaft Bearing Diameter 23 mm (0.906 in.)
Camshaft Bearing Width
4BY
15.85 -0.08 mm
(0.6240 -0.003 in.)
6BY
18.85 -0.08 mm
(0.742 -0.003 in.)
Valve Seat Angle 45°
Outer Correction Angle 15°
Inner Correction Angle 60°
Valve Seat Width - Intake
1.0 +0.1 mm
(0.039 +0.004 in.)
Valve Seat Width - Exhaust
1.2 +0.1 mm
(0.047 +0.004 in.)
Valve Seat Surface Outside Diameter - Intake
24.5 +0.1 mm
(0.965 +0.004 in.)
Valve Seat Surface Outside Diameter - Exhaust
24.4 +0.1 mm
(0.961 +0.004 in.)
Camshaft
Thrust Bearing Width
19.000 +0.01 mm
(0.748 +0.004 in.)
Radial Runout
0.040 - 0.060 mm
(0.0015 - 0.0024 in.)
Axial Play
0.02 - 0.150 mm
(0.0008 - 0.0059 in.)
Valves
Head Diameter - Intake
25.9 ±0.1 mm
(1.020 ±0.004 in.)
Head Diameter - Exhaust
25.9 ±0.1 mm
(1.020 ±0.004 in.)
Stem Diameter - Intake
5.92 ±0.02 mm
(0.233 ±0.0008 in.)
Stem Diameter - Exhaust
5.92 ±0.02 mm
(0.233 ±0.0008 in.)