P 1
7
/ 1
8
R
epair
[4] DISASSEMBLY/ASSEMBLY
[4]-14. Engine block (cont.)
(1) Piston can be assembled in either direction.
Apply a little amount of Makita grease N No. 2 to the needle bearing of Crank shaft assembly in advance.
(2) Insert Piston pin through Piston and Crank shaft, and fix it with Clips by using an awl (Clip has no direction).
(3) Piston rings have their directions and each different shapes as drawn in
Fig. 72
.
First, install Piston ring 34, and next, install Piston ring (second) 34, then finally install Piston ring (top) 34.
The piston ring 34 (fast one) consists of three part ; top ring, middle ring and bottom ring.
Top ring and bottom ring have a clearance and the distance of each clearance point must have 120° angle.
Piston ring (top) 34 and Piston ring (second) 34 consist of single part and the distance between their clearances must
have 180° angle when they fixed into the grooves on the piston.
Note
: Piston rings are easy to break. Do not enlarge them too much when fixed.
(4) Assemble Cylinder block assembly.
Degrease the matching surface of Cylinder block and Crank case (Refer to
Fig. 73
), apply ThreeBond 1215
on the Crank case side.
Note
: The layer of ThreeBond 1215 has to be thin so as not to enter into the oil route in Engine and get clogged.
Apply 4stroke oil to the contact surface of Piston and Cylinder.
While holding Piston rings, Install the assembled part of Piston into Cylinder block.
(5) Fasten Cylinder block assembly by tighten the screws in crisscross pattern.
Fig. 72
Fig. 73
ASSEMBLING
Piston ring (top) 34
Piston ring (top) 34
The center is expanded.
Piston top end
Bottom layer
Middle layer
Top layer
The matching surface: emphasized by black color
Piston ring (second) 34
The bottom is wider than the top.
The position between two
clearances must be
at 180°
opposite point.
Difference of the clearance
should be
120°.
Cross section of Piston
Piston ring (second) 34
Piston ring 34
Piston ring 34
It consists of three layers.
The top layer and the bottom layer have a clearance
as drawn above.
Clearances should not be
overlapped each other.
Piston
