Power Unit - TOHATSU MFS 4 Service Manual

1. Special Tools .............................. 5-2
2. Parts Layout .............................. 5-3
Engine .......................................... 5-3
Magneto.......................................... 5-4
Cylinder & Oil Pan ........................... 5-6
Cylinder Head & Valve & Cam Shaft ... 5-8
Piston & Crank Shaft ........................ 5-10
Recoil Starter ................................. 5-11
Top Cowl ....................................... 5-12
3. Inspection Items ........................ 5-13
1)Inspection of Compression Pressure
2)Inspection of Valve Clearance ......... 5-14
3)Removing Power Unit ..................... 5-16
4)Removal and Disassembly of
Crank Case Head ........................... 5-17
5)Inspection of Crank Case Head ......... 5-18
6)Assembly of Crank Case Head ......... 5-18
7)Installation of Crank Case Head ...... 5-18
8)Disassembly of Power Unit............... 5-19
9)Removal of Rocker Arm .................. 5-22
10) Removing Cylinder Head............... 5-23
11) Inspection of Rocker Arm and Pivot 5-23
12) Inspection of Push Rod Plate ......... 5-23
13) Inspection of Push Rod ............... 5-23
14) Disassembly and Inspection of
Oil Feed Pump ........................... 5-23
15) Disassembly of
Cylinder and oil pan ..................... 5-26
16) Disassembly and Inspection of
Breather Chamber ..................... 5-28
17) Inspection of Lifter........................ 5-28
18) Inspection of Cam Shaft ............... 5-29
5

Power Unit

19) Inspection of
Piston Outer Diameter .................. 5-30
20) Inspection of
Cylinder Inner Diameter ............... 5-30
21) Inspection of Piston Clearance ...... 5-30
22) Inspection of
Piston Ring Side Clearance............ 5-31
23) Inspection of Piston Rings ............ 5-31
24) Inspection of Piston Pin ............... 5-32
25) Inspection Connecting Rod
5-13 Small End Inner Diameter ............ 5-32
26) Inspection of Connecting Rod
Big End Inner Diameter ............... 5-32
27) Inspection of Connecting Rod
Big End Side Clearance ............... 5-33
28) Inspection of Crank Shaft ............ 5-33
29) Disassembly and Inspection of
Oil Pan .................................... 5-34
30) Removal of Valves and Springs ...... 5-35
31) Inspection of Valve Springs............ 5-35
32) Inspection of Valve ..................... 5-36
33) Inspection of Valve Guide ............ 5-36
34) Inspection of Valve Seat ............... 5-37
35) Correction of Valve Seat ............... 5-38
36) Installation of Valves..................... 5-41
37) Installation of Piston and
Connecting Rod........................... 5-42
38) Assembly of Cylinder Oil Pan ......... 5-43
39) Installation of Cylinder Head ......... 5-45
40) Installing Flywheel........................ 5-47
41) Installation of Power Unit ............... 5-50
5