test cdi and ignition coil using fluke meter?

GoldenMotor.com

motor_bike_fanatic

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I'm having electrical problems and I don't have any testing equipment. a buddy of mine has a fluke meter. can anyone tell me if we can test the cdi and the coil with a fluke meter and also how to do it and what readings we should look for?
 

Fulltimer

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I'm having an electrical problem also. I checked the CDI with a volt meter but the reading was so fast I couldn't read it. All I could tell was it was putting out something. I have no idea what a Fluke Meter is. But, I will find out thanks to everything being on the internet!

Terry
 

The_Aleman

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Jul 31, 2008
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A Fluke meter is the industry standard. If you don't have a Fluke, you might be considered a fluke yourself in some circles lol

Gar, elitists. But, I would also like to hear from electrical gurus a proper way to test CDI and magneto and then this thread be tagged so :D
 

Venice Motor Bikes

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Mar 20, 2008
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Electrical problems on HT's are something I rarely have... I never install the kill button & remove those wires; I also completely remove the white wire from the engine & I remove the plug ins & solder & heat shrink the blue & black wires.
I always recommend to people that they use battery powered lights & NOT run lights (or anything) off the white wire because I feel that it can create a weaker spark.
On the rare occasion that a bike loses spark?. it's always the magneto inside the engine that went bad. ;)
 

2door

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I have no use for digital meters. Especially when trying to read voltage. I rely on my venerable Simpson 260 analog VOM that is rock steady and reliable.
Here's some ohm readings that have proven to be reasonably accurate for testing the electrical components. Readings can vary but if you're in the ball park you should be good to go.
And Barley Awake is right, Fluke is an overpriced product with a word-of-mouth reputation. Simpson is the better choice.

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

Tom
 
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motor_bike_fanatic

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well, my buddy doesn't have a simpson, he has a fluke. I don't have money to buy testing equipment. who cares if its overpriced? I didn't pay for it. as long as it works, that's all that matters.
 

Fulltimer

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I have no use for digital meters. Especially when trying to read voltage. I rely on my venerable Simpson 260 analog VOM that is rock steady and reliable.
Here's some ohm readings that have proven to be reasonably accurate for testing the electrical components. Readings can vary but if you're in the ball park you should be good to go.
And Barley Awake is right, Fluke is an overpriced product with a word-of-mouth reputation. Simpson is the better choice.

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: Mine is good
2) Check ohms between BLUE wire and WHITE wire. Should be around 300-400 ohms.: Mine is good.

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): I have 3.69
2) Positive lead on BLACK wire and Negative lead on BLUE wire. Should be about 130-150 K-ohms: I have .367
3) Positive lead on Spark Plug wire and negative lead on BLUE wire. Should read between 135-155 K-ohms: I have 2.91

Switch to Low Scale 20K
4) Measure between Spark Plug wire and Black lead. Should be about 2.5 - 2.7 K- ohms: I didn't check

Tom
I know, I know...you don't like digital meters. :) But that is what I have. In bold above are my results. What is the problem? I have a new CDI with new spark pug and cable. But the motor will not start.

Terry
 
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2door

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Terry,
I'd start with a new CDI. Your readings make me a little suspicious of it.
The readings I posted are a result of an average taken by testing five different CDIs and Magnetos. They were all tested on the same engine and proved to be good.
Tom
 

Fulltimer

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I just checked by pulling the plug and laying it on the cylinder head. I have spark. Lets see, I have good gas, spark and air...ain't much else needed! If I have spark it isn't the kill switch or CDI. I varied the spark plug gap between .020 and .030 with no difference too. I used the old plug and a new one. I'm at a loss!

I called a friend of mine and he is going to look at it. He builds motorcycles. Maybe he will see something that I'm just not seeing. Like the old saying...you can't see the forest for the trees type of thing.

Terry
 

Al.Fisherman

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Re: Bench Test of CDI

Here's a quick way to bench test a CDI module, be careful, HIGH VOLTAGE.


I like it.....

The magnet (itself) has nothing to do with weather the Magneto (coil) will fire or not (although you need it). It's just a magnet mounted on the shaft, opening and closing the field. When was the last time one saw a magnet go bad. If you want to check it, take a screwdriver and touch the magnet itself. My first suspect would be in the timing of the engine. These are very simple engines, easily to diagnose problems.

What I would do, but that's me.

1. Disconnect the kill wire switch. Still no spark?
2. Make sure the the electrical connections are correct. This includes removing the white wire completely. Re solder the blue wire (cold solder joint), and at the same time check the timing (broken key), make sure the blue wire is not grounding anywhere. Check the wires themselves. Check the terminal, make sure it has a good ground contact on the magneto. on the black wire
3. Checking engine timing...
Magnetto pictures by Ron-Becker - Photobucket
4. I made a small LED test light to see if the magneto puts out voltage. Bought at Radio Shack

5. Then on to the CDI and check as Tom described.
6. The spark plug or wire might be defective. Check them also.
7. Then I'd replace a part, as needed.
 
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2door

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Terry, by any chance did you remove the magneto rotor (magnet) from the shaft? It can be installed backwards and will keep an engine from running if it's on wrong. I believe Aleman and Dave have some photos of the right and wrong way to install the rotor. One of them will probably speak up now that I've mentioned it.
Tom
 

Goat Herder

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There is also the age old scenario.... You can have spark but if it's too weak to go into the compressed atmosphere of the engine cylinder? Causes a internal shorting out in the cdi. Cracked spark plug. Magneto putting out to low of voltages etc. Electricity is lazy so to speak it will always find the shortest path to ground.

These are things that can be measured with scopes.. How ever there is a spark plug tester that can be used to measure how much voltages is reaching the plug. Spark Plug Tester - YouTube The gap is adjustable to represent voltage. X amount of available voltage will jump X amount of a gap.