No spark - CDI to blame?

T

TedStriker2

New Member
I've got another sparkless wonder, and changing the plug and plug wire didn't help. I took the recommended ohm readings, but I could use some help interpreting the results.

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
My reading: 1.8

2) Check ohms between BLUE wire and WHITE wire. Should be around 300-400 ohms.
My reading: 325

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)
My reading: no activity

2) Positive lead on BLACK wire and Negative lead on BLUE wire. Should be about 130-150 K-ohms
My reading: 295

3) Positive lead on Spark Plug wire and negative lead on BLUE wire. Should read between 135-155 K-ohms
My reading: 305

Switch to Low Scale 20K
4) Measure between Spark Plug wire and Black lead. Should be about 2.5 - 2.7 K- ohms
My reading: 5

The CDI readings are all high, but I don't know if they're high enough to clearly indicate the CDI is my problem. If anyone out there can say for sure, I'd really appreciate it.
 
I would double check your blue and black wire connections and if the connection is solid, then make sure that the little wire soldered to the magneto frame is not corroded or detached. also make sure that your black ground wire connection to the magneto is tight and not corroded. If all is good, then, most likely a bad magneto. I would try to have an extra magneto and cdi on hands at all times just so you have something to test with ya know. Hope you get it workin again!
 
Thank you both for the advice. This is actually my first bike and it has never run. I'd be a little more hopeful if it had. But if the CDI readings are normal I'll look closer at those wire connections. I'll order an extra CDI and magneto, but I probably won't get them until after Thanksgiving. I'll post back if I figure out what the problem is.
 
The meter readings given for the magneto would indicate that it is OK.
If you are brave, here's another way to test the magneto:
Strip a little insulation from both the black and blue wires and hold them between your fingers, crank the bike and you should feel a little tingle.
 
I hooked up my multimeter to the leads from the magneto and measured some voltage while cranking the pedals. Between my erratic cranking and the erratic numbers, I don't know if the voltage was normal -- but that accomplishes the same thing as grabbing the wires, right?
 
Yes, if your meter indicates some output from the blue and black wires while cranking, then your magneto is OK.
 
I never hooked up the kill switch, and the other wire connections seem OK. What I just discovered is that sometimes when I crank the pedals, the piston doesn't move and the magnet doesn't spin. That may explain the erratic voltage readings off the magneto. If I push the piston all the way back down it'll work normally for a few turns, but eventually the piston gets to the top and stays there, despite my cranking. I can't imagine what is going on inside the engine for that to happen. I'm searching the forums, but no luck so far.

EDIT - Turns out the clutch is slipping. I had a freaky tight clutch spring which I did everything to loosen, short of taking the whole engine apart (the flathead screws holding it together were self-destructing rather than turning, so I gave up). I wound up loosening the flower nut, and apparently I loosened it too much. I'm hot on the trail now though!
 
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FIXED IT! Of course, I also broke it. But I'm getting plenty of spark now. The moral of this story is to check whether your clutch is slipping.
 
I am always surprised when I read a thread and the bottom line turns out to be the person couldn't tell if their motor is turning over or not... Yet I read it over and over again....

No spark? Hmm, motor not turning over, there's your problem!

I'm not trying to insult you, it just surprises me that someone can miss the sound of compression and a motor turning over, or the lack there of. Like I said, it happens quite often...

I am into music quite a lot, play guitar etc, so my ear is tuned to listen to things. I use my ears quite a lot when riding and tuning my bike, you might be surprised how useful your ears are in diagnosing what you have going on with your motor. I can tell my speed, if she's four stroking, if something is coming loose, if the carb is not tuned well (and if the motor is turning over) all by just listening....
 
Not taking the magneto cover off to see whether it was actually spinning? I admit, that was a real forehead slapper. That should've been step zero, and I probably deserve some ribbing on that. Not hearing the piston "whoosh"? That's a lot more subtle. Remember I was cranking the engine by turning the pedals, and the bike drive train makes noise. Enough noise to obscure a sound that wasn't being made.

I just did my first test run of the engine, and it seems to be working great. Now I just need to hook up the kill switch and find someplace to practice riding - preferably without getting run over or annoying my neighbors.

Thanks again for all the help. This is a great forum.
 
TedStriker2 said:
Not taking the magneto cover off to see whether it was actually spinning? I admit, that was a real forehead slapper. That should've been step zero, and I probably deserve some ribbing on that. Not hearing the piston "whoosh"? That's a lot more subtle. Remember I was cranking the engine by turning the pedals, and the bike drive train makes noise. Enough noise to obscure a sound that wasn't being made.

I just did my first test run of the engine, and it seems to be working great. Now I just need to hook up the kill switch and find someplace to practice riding - preferably without getting run over or annoying my neighbors.

Thanks again for all the help. This is a great forum.
Click to expand...

Congrats on getting her rolling!
I really wasn't trying to rib you, I think after you get more familiar with the motor you will understand better what I mean, when I pop the clutch and the motor turns over I can hear it even if its not firing, there's a purr there that isn't gonna come from clutch drag......
 
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