loosing spark

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grizadams

grizadams

New Member
Jul 23, 2012
90
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minnesota
My bike will run for a while then stall and won't run again for a while. What appears to be happening is I loose spark. Could it be that it's getting flooded out and then the plug gets wet and then won't spark? This doesn't make sense to me because when I swap another plug in it still won't spark. I also resolderd all connections.

I've got the kill switch disconnected. So that can't be causing the problem.

I had the thought it could be vapor lock, but why no spark then.

The only other thought I had is I just put a new air cleaner on but that can't be related to spark.
 
tooljunkie

tooljunkie

Member
Apr 4, 2012
663
5
16
Manitoba,Canada
the connections inside the cover -the factory soldered joits can fall apart.
otherwise its the cdi or the lamination with the winding on it.
if water got in there that would explain things.
 
grizadams

grizadams

New Member
Jul 23, 2012
90
0
0
minnesota
I resoldered the joints tonight.
I did drive home last night and it was sprinkling out. That does make sense. It's kind of like a coil in a car that is crack and when it gets wet you loose spark.
 
dragray

dragray

New Member
Mar 10, 2012
278
2
0
Indiana
do you have anything hooked to the white wire coming from the engine (like a headlight) ?

it's not the coil on a car engine that will give you this problem.
it's the distributor cap.
if it's cracked & moisture gets in it, you won't get any spark.
 
KCvale

KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
Where is your CDI mounted?
They don't like heat. Actually no electronics like heat but that is a symptom of heat, the warms up and it affects spark and won't run again until it cools off.
Note the magneto can suffer from this as well but near as bad.
 
M

mario

New Member
Jun 7, 2012
7
0
0
canada
I have a problem starting my 80cc engine when it was fine before with the exception that every now and then the engine would stall but now it wont start at all. What is happening is that when i ride down hill with the clutch disingaged there is no sound but as soon as i ingage the clutch the motor sounds like it want to start but what i really think is happening is the pressure from the piston that makes that noise that it seems it wants to start but as soon as i disingage the cutch, the engine dies and its no longer building pressure. I checked the spark plug out ot the motor and grounded it but when i crank the engine i cannot see a spark. I sospect the coil or the magnatron, I checked the coil and magnatron windings for resistance and the coil had about 340 ohms between the blue and white wires and the magnatrom has 6.8 kilohms from black to spark plug wire and 16.6kilohms from blue to black wire. If anyone has any ideas i would really appreciate the help because i miss riding my bike. Thanks in advance MC
 
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2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
Try this :

Use Low Ohm-Meter Scale About 200 Ohms

Magneto Coil

1) Check Ohms between BLACK wire and WHITE wire. Reading should be around 2 Ohms
2) Check ohms between BLUE wire and WHITE wire. Should be around 300-400 ohms.

CDI

Use Ohm Meter High Scale About 200-K
1) Positive lead on BLUE wire and Negative lead on BLACK wire should read infinite (no activity)
2) Positive lead on BLACK wire and Negative lead on BLUE wire. Should be about 130-150 K-ohms
3) Positive lead on Spark Plug wire and negative lead on BLUE wire. Should read between 135-155 K-ohms

Switch to Low Scale 20K
4) Measure between Spark Plug wire and Black lead. Should be about 2.5 - 2.7 K- ohms

Personally I prefer to use an analog meter as opposed to a digital. I have a great old Simpson 260 that leaves no room for doubt, unlike most digitals that bounce all over the scale. But then I'm a confirmed dinosaur so whatdaya expect? :)

Tom
 
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grizadams

grizadams

New Member
Jul 23, 2012
90
0
0
minnesota
so if I connect the positive lead on blue and the negative on black for the cdi and I get activity what does that mean?
 
KCvale

KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
It means your meter is trying to power the CDI, Ohm scale uses power to measure resistance. Just test as shown above.
 
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