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  #1  
Old 27-05-2018
RMXhammy RMXhammy is offline
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Simple multimeter question. No spark diagnostics

Ok, electrics are my weak point. I'm diagnosing a yz125 with no spark

I have a multimeter with settings of 200, 2000, 20k, 200k and 2000k ohm,

My manual states to use settings for the various tests of

ohm x 1 (primary coil)

k ohm x 1 (secondary coil, plug cap)

Ohm x 100 (cdi pickup coil and charging coil 1)

Ohm x 10 ( charging coil 2)


No idea what settings I should use on the multimeter for each test and/or if I also need to multiply or divide my readings by something to get the right result











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  #2  
Old 27-05-2018
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Quote:
Originally Posted by RMXhammy View Post
Ok, electrics are my weak point. I'm diagnosing a yz125 with no spark

I have a multimeter with settings of 200, 2000, 20k, 200k and 2000k ohm,

My manual states to use settings for the various tests of

ohm x 1 (primary coil)

k ohm x 1 (secondary coil, plug cap)

Ohm x 100 (cdi pickup coil and charging coil 1)

Ohm x 10 ( charging coil 2)


No idea what settings I should use on the multimeter for each test and/or if I also need to multiply or divide my readings by something to get the right result





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The settings on your multimeter are just a scaling so you get the best resolution on your display. The idea is the use the setting that your reading will just fit within.

I find the suggetsed settings in the manual a little confusing but my best guess would be as follows - the primary coil value will be somewhere between 0 and 10 ohms so use the 200 setting on your mulimeter. The secondary coil, plug cap use the 2000 or 20k setting, cdi pickup use the 2000 setting and the charging coil ise the 200 setting.

I dont know much about auto electrics so could be way off.

Edit - i just saw the picture you posted from the manual and it states the primary coil value should be around 0.2 to 0.3 ohm so use the 200 setting on your meter. Check your manual for the other expected values and set your meters ohm range so that it is greater than the expected reading - hopefully that makes sense.
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Old 27-05-2018
RMXhammy RMXhammy is offline
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Thanks, that's kind of what I was thinking with my experimenting. I was using the 200 setting for any expected reading of less than 1. This also makes me think this multimeter isn't precise enough as it'll only give values to the nearest decimal place


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Old 27-05-2018
Muppet Muppet is offline
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You need to move your black lead into the "com" port mate.
Then as mentioned, use the 200 scale.
Older, cheaper electronic meters don't read low values very accurately so don't stress too much straight sway if you're a little off what you think you should be.
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  #5  
Old 27-05-2018
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What year Yz125 Hammy?

Im assuming you have done all the basic stuff first?

And yeah cheapo multimeters are a big pitfall when it come to getting accurate reads
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Old 27-05-2018
RMXhammy RMXhammy is offline
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Quote:
Originally Posted by gasgasman280 View Post
What year Yz125 Hammy?



Im assuming you have done all the basic stuff first?



And yeah cheapo multimeters are a big pitfall when it come to getting accurate reads


I've got two of them. The non-starter is a 2008, and I've also been testing some components off a running 2007 to diagnose the fault through a process of elimination. Have done the following:


- no spark when reding the plug against the frame and kicking it over

- swapped plug from bad to good bike. Ok. Gets spark so plug is fine

- have swapped the cdi and ignition coil from the good bike to the non-starter (one step at a time). No change


- disconnected kill switch and repeated step 1. No change

- wd40 into all connections and blown out with air. No change

-have yet to put the cdi and coil from the non starter to the good bike to double check that they're ok

Now I've just realised why some of the diagrams didn't make sense and I've found the first connector leaving the magneto hiding up under the radiators

Reran some of my tests for charging coil 1 resistance (see picture)


Good bike: varying results from 200 to 1000 before the meter gives up and screen goes blank necessitating me turning it on and off again

Non-starter: no reading at all. Meter stays at 1

I'm not convinced of the meter accuracy given the large fluctuations on the good bike



Thinking this is either the problem or I find a better meter and retest again




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Old 27-05-2018
RMXhammy RMXhammy is offline
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As background, this bike has been faultless for over 2 years and then just lost power and stopped a few corners into a race. No spark since


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Old 27-05-2018
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Has your meter got a fresh battery??
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  #9  
Old 27-05-2018
RMXhammy RMXhammy is offline
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Simple multimeter question. No spark diagnostics

Quote:
Originally Posted by gasgasman280 View Post
Has your meter got a fresh battery??


Good point and I have no idea as it's a borrowed meter. I'll throw a new one in and check if I can't get hold of a better meter




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  #10  
Old 30-05-2018
RMXhammy RMXhammy is offline
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Ok, I have another multimeter and have finally got some consistent readings on the good bike that match the manual and confirmed these with a 3rd expensive meter temporarily in my possession

So going by the manual, one of the magneto tests on the non-runner shows no resistance at all (charging coil 1 test). So I assume my stator is stuffed? I don't have a puller or any other means to take the flywheel off at the moment to investigate further

Are stators repairable or are they a throwaway item once not working?


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