CDI Testing with a multimeter

[Carl Walichnowski]

I thought a good thread would be to how to test a CDI & Magneto with a multimeter. I know I currently have the issue of a potential CDI or Magneto that could be bad. For the inexperienced like myself I wasn't even aware you could even test either part with a multimeter. So it'd be great if those with the know how would provide some input on the subject so it's readily available. Please list what to test and more importantly and not so obvious what readings should we get from the multimeter?? Thx

 

[crassius]

several lists of test values were on the forum many years ago, and are probably still here - were of little use to folks since so many capacitors and rectifiers and transistors are involved

 

[Timbone]

Stator test: blue wire to black wire 320-380 ohms.

CDI test: red multimeter probe in black CDI socket; black probe to end of spark plug wire or to the output screw in the CDI. Optimal reading: 6.9k ohms.

I got all these figures from the experts on here.

 

[Carl Walichnowski]

That's great info. How about the readings for the magneto?

 

[Carl Walichnowski]

I did see a thread listing readings but the thread was several years old & the readings were varied. I hoped there was updates with the readings especially since new and improved CDI's have been made. If the multimeter provides such an unpredictable reading is there a tester that would work better?

 

[Timbone]

The magneto /stator (black wire to blue wire) should read 320-380 ohms.

 

[crassius]

CDIs are not 'new and improved' - readings vary because a meter with a larger battery will get more feedback effects from the capacitors

if you're wotrried about CDIs be sure to have a known good one on shelf - otherwise build a tester

 

[Carl Walichnowski]

So they don't sell a quality tester to do the job? I'm worried about my CDI &/or Magneto cause I'm not able to fire my motor up and I'm not getting any spark with a new plug. Where do you buy your CDI's from? I'm looking for a good one but I'm not trying to spend a fortune. Thx

 

[Carl Walichnowski]

I
n addition I thought Grubee started providing better CDI's in their kits since 05, guess they just started offering new ones and didn't reenvent the wheel.

 

[crassius]

only thing I've seen is the change from the plastic caps that often broke to the rubber ones that last longer - unfortunately, most seem to be going back to gluing the plug wire into the CDI which makes it really hard to replace it

old mags used to be 250ohms and were hard to start, then came 350ohm mags that were better, later came the 480ohm mags that blew out a lot of CDIs, so most are back to 350ohms now

I get most of mine by selling replacement motors and putting rest of kit on shelf for repair parts - were I to order CDIs, I'd just go with what's cheapest from a dealer that is good.