Torque Values (Tightening Force) - Honda Motorcycle Service Manual

GENERAL INFORMATION
TORQUE VALUES (Tightening Force)
When t w o or more parts are connected by a fastener, their
connection should not be affected by external forces; i.e. there
should be no gap between the parts which are fastened
together. The first priority of threaded fastener connected
parts is the state of being tightened with a sufficient force.
When any tightening force is sufficient for the intended func-
tion,
it
is called "proper tightening force".
The tightening force of one bolt is equal to bolt axial tensile
strength. Bolt tightening force is, therefore, often called "bolt
axial force".
A decrease in tightening force (initial tightening force) due to
the passage of time, external forces, or vibration applied
during use is called "fastener loosening". Even when the
initial tightening force was correct, loosening may cause it t o
decrease in later use, finally damaging some parts. As a
countermeasure against fastener loosening, retightening is
carried out after a certain period of time. Periodically tighten-
ing wheel spokes is an example of this operation.
F: TIGHTENING FORCE
BOLT AXIAL FORCE
As mentioned earlier, the most important point in fastener
tightening is the tightening force. The problem is that this
tightening force (axial tension) is difficult to measure.
Using a predetermined tightening torque is, therefore, the
most common method of controlling fastener tension.
Proper tightening forces are specified according to fastener
strength, strength of fastened parts and intensity of external
forces. Tightening must be carried out in strict accordance
with this specification, especially at important points. Tighten-
ing a connecting rod bearing cap with a stronger force than is
proper, for example, will deform the tightened part (bearing
cap) slightly and cause the oil clearance for the bearing to
become smaller than specified, which may lead to the bearing
seizing. An insufficient tightening force, on the other hand.
may allow the nuts or bearing caps to loosen and fall off during
engine operation, leading to serious engine trouble.
Y
-
X
-
TIGHTENING TORQUE
4
OIL CLEARANCE
L
NG
REDUCED OIL
CLEARANCE
BEARING CAP CRANKSHAFT
Date of Issue: March,
1995
1-10
0
HONDA MOTOR CO.,LTD.