Yamaha XS650 Series, Shop Manual

Page: 92 / 215

turned on and the crankshaft is not
turned, the protective circuit stops
current flow to the primary coil within
a few seconds. When the crankshaft is
turned over, the current is turned on
again by the signals generated by the
pick-up coils.
NOTE:
Even though two spark plugs fire at the same
time only one cylinder is on the compression
stroke at a time. The other cylinder is
on
the
exhaust stroke and the spark in that cylinder
has no effect.
- C A U T I O N :
Do not run the engine without any spark
plug cap(s) in place. Due to the high sec-
ondary voltage, it is possible to damage the
internal insulation of the secondary coil.
4. Troubleshooting/Inspection
a. The entire ignition system can be
checked for misfire and weak spark using
the Electro Tester. If the ignition sys-
tem will fire across a sufficient gap, the
engine ignition system can be considered
good.
If not, proceed with individual
component tests until the problem is
found.
1) Warm up engine thoroughly so that all
electrical components are at operating
temperature.
2) Stop the engine and connect the tester
as shown.
Start the engine and increase the spark
gap until misfire occurs. (Test at various
rpm between idle and red line.)
Minimum spark gap: 6 mm (0.24 in)
Do not run engine neutral above 6,000
for more than 1 or 2 seconds.
b. If the ignition system should become
inoperative, the following troubleshoot-
ing aids will be useful.
Check battery for
voltage and
specific gravity
OK
Check fuse and fuse
connections
Weak
or
open or
Check resistance of
Primary: 2.5
Check pick-up
coils for resistance
Pick-up coil:
7 0 0 R 20%