since the motorcycle last started easily. For in-
stance, was the weather dry then and is it wet
now? Has the motorcycle been sitting in the
garage for a long time? Has it been ridden
many miles since it was last fueled?
Has starting become increasingly more dif-
ficult? This alone could indicate a number of
things that may be wrong but is usually
associated with normal wear of ignition and
While it's not always possible t o diagnose
trouble simply from a change of conditions,
this information can be helpful and at some
future time may uncover a recurring problem.
Although it is the second most likely cause of
trouble, fuel delivery should be checked first
simply because it is the easiest.
First, check the tank t o make sure there is
fuel in it. Then, disconnect the fuel hose at the
carburetor, open the valve and check for flow
(Figure 2). If fuel does not flow freely make
sure the tank vent is clear. Next, check for
blockage in the line or valve. Remove the valve
and clean it as described in the fuel system
If fuel flows from the'hose, reconnect it and
remove the float bowl from the carburetor,
open the valve and check for flow through the
float needle valve. If it does not flow freely
when the float is extended and then shut off
when the flow is gently raised, clean the car-
buretor as described in the fuel system chapter.
When fuel delivery is satisfactory, go on to
the ignition system.
Remove the spark plug from the cylinder and
check its condition. The appearance of the plug
is a good indication of what's happening in the
combustion chamber; for instance, if the plug is
wet with gas, it's likely that engine is flooded.
Compare the spark plug t o Figure 3. Make cer-
tain the spark plug heat range is correct. A
"cold" plug makes starting difficult.
After checking the spark plug, reconnect it t o
the high-tension lead and lay it o n the cylinder
head so it makes good contact (Figure 4). Then,
with the ignition switched o n , crank the engine
several times and watch for a spark across the
plug electrodes. A fat, blue spark should be
visible. If there is n o spark, or if the spark is
weak, substitute a good plug for the old one
and check again. If the spark has improved, the
old plug is faulty. If there was no change, keep
Make sure the ignition switch is not shorted
t o ground. Remove the spark plug cap from the
end of the high-tension lead and hold the ex-
posed end of the lead about
inch from the
cylinder head. Crank the engine and watch for
a spark arcing from the lead to the head. If it's
satisfactory, the connection between the lead
and the cap was faulty. If the spark hasn't im-
proved, check the coil wire connections.
If the spark is still weak, remove the ignition
cover and remove any dirt or moisture from'the
points or sensor. Check the point or air gap
Reference Data at the beginning of the book.
If spark is. still not satisfactory, a more
serious problem exists than can be corrected
with simple adjustments. Refer to the electrical
system chapter for detailed information for
correcting major ignition problems.
o r the lack of it
least likely cause of starting trouble. However,
if compression is unsatisfactory, more than a
simple adjustment is required to correct it (see
the engine chapter).
An accurate compression check reveals a lot
about the condition of the engine. T o perform
this test you need a compression gauge (see
Chapter One). The engine should be at
operating temperature for a fully accurate test,
but even a cold test will reveal if the starting
problem is compression.
Remove the spark plug and screw in a com-
pression gauge (Figure 5). With assistance, hold
the throttle wide open and crank the engine
several times, until the gauge ceases to rise.
Normal compression should be 130-160 psi, but
a reading as low as 100 psi is usually sufficient
for the engine t o start. If the reading is much
lower than normal, remove the gauge and pour
about a tablespoon of oil into the cylinder.
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