TOHATSU MFS 8B Service Manual page 144

1. Measure cylinder inner diameters (D1 to D6) at
and in crank shaft directions
respectively), and in crank web directions
respectively).
Cylinder Inner Diameters (D1 to D6) : Standard Value
55.00 mm (2.1654 in)
Functional Limit :
55.06 mm (2.1677 in)
Maximum value – Minimum value = 0.06mm
If serviceable limit is exceeded, replace, or
bore to ø55.5 ± 0.01mm and hone, and replace
pistons and piston rings with oversize parts.
Note : Measure at the maximum wear points.
2. Check inner surface of cylinders.
If any flaw is found, remove by using sand paper in number
400 to 600 range.
1. Obtain piston clearance through calculation described
below.
If piston clearance is over specified limit, replace cylinder
block, or piston and piston rings as a set, or both cylinder
block, piston and piston rings.
Piston clearance = Cylinder inner diameter
(maximum) - Piston outer diameter
0.020 - 0.055 mm (0.00079 - 0.00217 in)
Functional Limit :
0.150 mm (0.00591 in)
1. Measure piston side clearance. Replace piston and piston
rings as a set if the clearance is over specified value.
Piston Ring Side Clearance :
Top Ring
Second Ring
Oil Ring
Functional Limit :
Top Ring
Second Ring
Oil Ring
5-40
(D1, D3 and D5
(D2, D4 and D6
: 0.04 - 0.08mm (0.0016 - 0.0031 in)
: 0.03 - 0.07mm (0.0012 - 0.0028 in)
: 0.05 - 0.15mm (0.0019 - 0.0059 in)
: 0.10 mm (0.0039 in)
: 0.09 mm (0.0035 in)
: 0.18 mm (0.0071 in)
,
15mm (0.6in)
35mm (1.4in)
55mm (2.2in)
Crankshaft direction
Crank web direction
4st 8/9.8 2016