Motorcycle Repair/1978 Kawasaki ke175 Spark
QUESTION: Im working on this bike for a friend and the spark comes and goes. One minute it will be running fine the next it dies and there isnt spark any more. Iv tried a different CDI and coil with no luck. I hooked my test light to the pulsar and the light flashes when kicked over. I dont know what kind of voltage I should expect out of the coil but there is some coming out of there.
ANSWER: Hi Erik,
The voltage on the pulse or signal coil will be very low like
maybe 1 volt. If you were connected to the charge coil
or the exciter coil the voltage would be higher.
If the spark is quitting off and on it might be a few different
things. Have you verified the engine stop button is
not shorting out the black/white CDI wire except
when it is supposed to?
The ignition switch could also be grounding
out the black/white CDI wire.
The solution is to isolate the black/white
wire from the CDI for testing.
Next is the flywheel magnetism, it might be
rusted inside and have weak magnetic properties.
The exciter and pulse coils are together
on the right side of the magneto.
The coil on the left side is for lights and charging.
The exciter has 126-190 ohms on the white/red to black wire.
The pulser or signal coil has 24.9-37.3 ohms on the white/red to blue wire.
If these coils quit when warm they have a broken
connection inside somewhere.
You can either replace or rewind them with the same
size wire and the same number of wraps.
You can try checking the coils ohms when cold and then when hot to
see if it varies alot or not.
Also check your spark plug cap, wire, and plug for defects.
Use NGK spark plugs as others will foul so bad they will stop working
sometimes very quickly.
See if the spark will jump a gap of about 1/4" or 5mm.
Check the ignition coil and CDI unit ground connections.
Some coils need a clean frame ground to work,
same with the magneto coils.
Use some electronic spray cleaner on all connectors as
old connections always have some corrosion you can't really
see very well.
---------- FOLLOW-UP ----------
QUESTION: I checked the exciter and its at 170 ohms so that seems ok but the pulsar coil has like 1.7 ohms so im assuming that it needs replaced. How do I go about rewinding these? It appears that there is some sort of cloth over the coils with some waxy type stuff on top of that. Im fairly handy with a soldering iron but I dont have a clue about how to do this or where to get the wire. Thanks for the info!
ANSWER: Your pulser coil should have a small voltage pulse about 1 volt
when you kickstart the bike.
If you get no voltage spike at all then it might be shorted internally.
The ohms readings may indicate a short circuit in the pulser coil.
The wire you would need to rewind is called "magnet wire"
You must get something with the same or nearly the same
wire diameter. You will need to count how many wire wraps
are on the old coil as this needs to be close to the same or you
can wrap it until you get the proper ohms reading, around 35 ohms.
Search ebay and internet for the wire. You want it to be wire
with a thin coating of shellac or insulation so the wires
do not touch each other inside the coil.
Not as hard as it sounds just time consuming wrapping the wire.
The cloth and wax are just there to cover and seal the coil up
so vibration doesn't damage it.
Watch which way the wires are wound on the coil as well and
wrap the new wire in the same direction.
It has to be wrapped tightly to be able to fit under the flywheel.
Clean and check the flywheel magnets as well.
It might be easier to look for a replacement or a used one but
it can be interesting to experiment if you think the coil is faulty.
If you have access to another coil you could get the ohms
readings from that to see if they vary.
Hopefully you can pinpoint the problem without replacing
too many parts.
---------- FOLLOW-UP ----------
QUESTION: Ok I did unhook the kill wire (black and white) and it was still having the same problem. The cap and spark plug are good (ngk plug)The spark is extremely weak so I thought I'd be Mr. save money and tried unwinding the coil. I couldn't get the dang wax and paper off without damaging the magnet wire. Since the wire then had a couple breaks then I didn't know which direction it was wound, the more I unwrapped the more I started to doubt my abilities. Well about half way through that I decided to buy a used one that is about the only thing I havn't replaced so it should be the ticket. Its a dang good thing I knew a guy with the coil and CDI so I didn't have to buy those also. I hate just throwing parts at this thing but I don't see what else could be wrong with the ohms reading I had.
If you get stuck just try winding the pulser until it reads about
30 ohms. The wire direction will not be a big issue as they
output AC voltage anyway. As long as the CDI gets a small
voltage pulse it should work. The coil is just a standard
coil of wire coated with wax or epoxy.
It is difficult to pinpoint the problem when parts are scarce.
Here is a diagram link that should suit your bike's ignition system:
Sometimes when ohms readings look good and there is no
spark you have to resort to parts replacing to narrow it down.
Check all wiring and connectors for good continuity
as many good parts sometimes get replaced when they
Let me know if I can do anything to help.