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Just bought Multimeter, how do I test my stator, cdi, and coil?

Joined
Jan 12, 2007
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#1
Noob question....here goes...

My bikes doesn't have spark (79' YZ250). A friend told me to pick up an ohms meter or multimeter so I can test the parts so I did just that. This is the one I bought (hoping this might help): http://www.sears.com/sr/javasr/prod...=Automotive+Testing+Equipment&pid=00920926000

The only problem is im not sure how to use it. I read the directions but they don't really help me that much because ive never used one before. So, here is my question: How do I use it to test my stator, cdi, and coil?

Here is what I am looking for:
-What setting should my multimeter be set on?
-What wires do I attach the multimeter to and where on those wires? (and what wires they are..ex: ground, etc)
-And what do the results/numbers on the screen mean?

If this helps, here is what the wiring looks like starting with the stator:

Stator: It has 3 wires coming out:
1) White w/ red stripe
2) Red
3) Brown

Those wires go to into the CDI

Then there are 3 wires that come out of the CDI box:
1) Black w/ white stripe
2) Black
3) Orange
There's also Black w/ Red Stripe wire - This one comes out but then loops and goes back in where it came from.

Those three wires go to the coil. The black wire and black w/ white stripe wire from the cdi go into a connector that gets screwed down (kind of like a washer) under one of the mounting screws for the coil. The orange wire from the CDI is connected to a black wire that goes directly into the coil.

Then there's the spark plug wire that comes out of the coil.


So...where do I start?

if anyone wants, i can take pictures of the parts too...in case it helps.
 
Joined
Apr 26, 2007
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#3
You'll be able to check the stator and coil, but possably not the CDI. As Fox points out, you really need the manual so you know where the numbers should be. Generally speaking, you'll be using the ohms (resistance) range on the meter. When using the ohms function, you must make sure that all power is removed from the circuit your testing or you'll toast the meter. Most modern meters are now fused, usually found in the battery compartment. The number displayed will be the resistance in ohms between the leads, but how it's read will depend on what range you're set to.

The ignition coil consists of 2 coils, the primary that connects to the CDI and the secondary that goes to the plug. The primary has relatively few turns so it will have very low resistance (<1 Ohm typ.). If there's a single wire going to it, it's checked between that wire and ground. If there's 2 wires, it would get checked between them. The secondary will have a lot of turns of wire so the resistance will be pretty high (10k-20k ohms typ.). The secondary is usually measured between the hot wire (the only wire if it's a single wire system, check the manual for dual) and the plug wire. Compare your readings to the specs in the manual.

Stators have multiple windings, some provide power and others trigger the CDI. As a result, the resistance values can range from less than 1 ohm to several hundred ohms. For this reason, you have to have the manual to know what wires go where and what values they should be.

For the CDI, sometimes the manual will have various resistance values between different pin combinations, and sometimes not. If it doesn't, if both the coil and stator check good, and all the wiring and connections are good, chances are it's the CDI.

The usual repair by remote control disclaimer applies: This applies to bikes in general and may or may not be applicable to yours. You need to get the manual for you bike for the specific values and procedures applicable to your machine.

Marc -
 
Joined
Apr 18, 2006
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#4
Bunya said:
When using the ohms function, you must make sure that all power is removed from the circuit your testing or you'll toast the meter.

Actually, the digital Multimeters are almost bullet proof as far as the volts and ohms ranges are concerned. About the only way you could hurt the meter is if you connected it to a really high voltage, in the thousands of volts range. An old analog (needle movement) meter is another matter....

If the meter has an "amps" range then there is a major opportunity for blowing the fuse. The amps measurement usually requires moving at least one of the meter leads to another jack on the meter. If you forget and leave it there and then try to measure voltage you will essentially short out the system, most likely blowing the fuse in the meter (which may or may not be easily replaced.....)

Rod
 
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Apr 26, 2007
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#5
It's been a few years since I bought a DVM but I've never seen one that didn't have a fuse for voltage protection in ohms. Many have a second fuse for the 10A range. If I didn't have so many laying around, I'd buy a new one that didn't mind 12v going into it in ohms just so I didn't have to worry about keeping a supply of .315A fuses around. Despite dancing with the wires for 30 years or so I still screw up and forget to switch ranges now and then and pop the fuse. Thankfully I've never had the meter in an amp range when trying to check voltage. Forget the meter, that could Chernobyl whatever it was I was working on even with a fuse in the meter.