Diminishing output from CDI - 30 Volts to 2 Volts
Hi
I'm having an odd problem with my 50cc GY6 that maybe someone here can help find the solution to. It's a no-spark situation, and here's what's going on - The stator is working normally, putting out it's 80 volts. The CDI is receiving the 80, but starts by sending 30 volts to the ignition coil, and that quickly drops to 2 volts over the course of a few seconds. The CDI is new and another new CDI was tried with identical results. The ignition coil is also new. The CDI has good ground, an additional ground wire has been spliced in just to be sure. Everything else on the bike is working normally. Lights, turns signals, horn, etc. The trigger coil is also new and working. I'd really like to get this bike back on the road ASAP, so any help is appreciated. |
check the reg/rectifier
All done in less than 3 pages and countless voltmeter readings |
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The power wire for the CDI does not pass through your regulator/rectifier. The R/R has nothing to with spark. Gradual loss of spark usually points to the pickup coil just above your flywheel. Should be a blue or blue/white wire from your stator. Voltage should be about .5v to 1.0v. An anomaly with the pickup coil is that after a few firings or when they get warm from running...they lose voltage because the coil is faulty or stator voltage to them is irregular or too low.. This means your CDI may not be firing at the proper time i.e. late, at which time some of the current in CDI's capacitor has bled off giving you a weak spark. So get out your multimeter and check the pickup coil voltage.
Glenn |
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New parts or not..many arrive unserviceable.. I order CDI's for example in lots of 10 from my wholesaler..and always 2-3 of those are dead on arrival. Chinese QC is not like Japanese..German or Italian QC. Lastly by trade I am not a certified mechanic..but a retired military medic..who later became a cardiac nurse..then gave that up to run a scooter parts/repair shop. It's just me so I get to be my own boss and everybody enjoys working for somebody they really like..lol..:D But..anyway..the above is my 2 cents. I see pickup coils fail often and they exhibit exactly what you describe. Lets hope it is a simple as that. Btw..what was the voltage you got from your pickup coil initially..then again after the spark weakened after a few cranks on the engine. If you see a voltage difference before and after that..well you pretty much have all the evidence ya need I would think..:hmm: Glenn P.S. Does the hot wire from the stator to your CDI also drop in voltage after a few cranks? Cause the stator is a coil too..so all the above things that affect a coil..will affect that coil as well.. |
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The stator seems fine, it's showing +/- 80Vac consistently measured from the red/black wire at the CDI connector. I'll have to measure the trigger tomorrow, I hadn't thought to check it in comparison to the CDI output. I don't know how useful my VM is going to be at measuring that small and brief of a voltage, but we'll see what happens. One other thing - What are the odds of the trigger problem being in the magneto rather than the coil itself? I've tapped it with a small screw and felt no pull from it at all.. |
If your volt meter is digital it will capture the tiny burst of voltage..analog meters can't..nor do they work for the spark impulse from your CDI as it all happens so quickly.. Anyway yes..when you notice your CDI voltage drop..IMMEDIATELY check the stator output voltage for the CDI.. Chances are it has dropped as well..hence the reason your CDI output decreases. Let us know what you find..
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Checked the trigger and it's showing a steady .1 vac with 185 Ohms. The stator is steady at right around 80 vac.
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http://49ccscoot.proboards.com/threa...park-condtions :tup: |
While looking into this, I've seen .05Vac about as often as I've seen .5Vac as the minimum useful output from the trigger coil. Knowing now that it's .5, I'd say the trigger coil is bad.
I've ordered another and will post again once it arrives and I get it installed. Meanwhile, a musical interlude... http://www.youtube.com/embed/5MtdIO23MKM |
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Any luck with your spark issue yet?:hmm:
Glenn |
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Now it isn't sparking again. What's odd is that the sator is now showing around 60Vac instead of 80. Only about .1/.2Vac is arriving at the ignition coil. I took the stator and magneto from another bike, put them on the bike I'm trying to fix and got the same results from the VM. This was with the trigger coil that was on the donor bike. So right now I'm out of ideas. The new trigger coil did produce a spark, the bike tried to start then suddenly, all on it's own, it's back to not sparking. |
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Glenn |
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A few weeks ago I did remove the wiring harness (which was very wet at the time) and let it dry out, then put lengths of marine heat-shrink tubing around every splice. The factory splices were only wrapped with a bit of electrical tape, so it seemed there was room for improvement. Also, I added and additional ground wire from the CDI's ground wire directly to the frame. My father was an electronics tech as well, he started on the in the Air Force then ended up repairing TVs and such. Thanks for your help! |
I wanted to add 2 other things that may or may not have anything to do with this. Occaisionally, the fuse would blow when I tried to start the bike. either when the key was turned or the start button pushed, I don't know which. But once a new fuse was ut in, the problem was gone. The second is that 3 or 4 times the CDI would suddenly fail. Again, once replaced things would go back to normal. Each of these happened maybe 3 times over a 6 month period.
Both these things would happen without anything else going wrong. |
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Anyway..enough of that..back to your scoot.. If a CDI or fuse is failing or blowing..you got a definite short or bad ground.. Did your replace the stator? Or check and sand it's mounting area..as they do often create a bad ground..It is simple whatever it is..usually is.. Hohodika ela seyiimee dachamosan bela ieta sik Ojibwa tayatoola momonagi dadanemuk <-- I am a Chippewa,we were eradicated for being savages, not mechanics. lol.. But we will figure this out my brother of the earth..because.. Jiloho bena atika aya tiseemie moyat esesana aha kota <-- We only become defeated when...we stop trying to defeat something....:nod: |
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A bad ground sounds likely, but where could it be? 2 stators are producing the same low voltage (60Vac). When I last tested it about a week ago it was putting out around 80Vac. I'll pull the stator tomorrow a give the contact areas a cleaning just to be sure, but up until this point there's been no problem with it. So far, the CDI, Stator, Regulator, Trigger Coil, Ignition coil and Spark Plug have all been replaced with no change resulting other than getting a spark for a while after the last trigger coil replacement (That is, when a new one was put in, right now the stator and trigger coil that are installed were pulled from another bike). The condition worsens over the course of a few seconds. The CDI's output starts at 20Vac and drops to 2. I think we can probably eliminate the ignition components as the source of the problem. That leaves...? The starter and ignition switches have been tested and showed that they were good. I checked the wiring harness visually and didn't notice anything wrong with it. The brake light switch? Something in the taillight? I think I might just end up replacing each part on it until it works! |
Ok, it's been a while but I've done some more work on it with no results. I replaced the stator/trigger coil with a brand new set as well as both handlebar switch sets. At this point the only electrical components that haven't been replace are the flasher and the starter motor.
Is it possible that the starter motor could be worn and not turning the engine fast enough to generate enough electricity? |
I just went out and tried starting the bike again after having harged the battery and I may have been on to something - The starter barely turned and gave a high pitched grinding/whirring sound. I'll dig up a new solenoid and try switching that out just because I have one, and I'll order a new starter just to cover that too.
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Put a new solenoid on it and there was no change. Ordered an new starter motor, it should arrive by Monday.
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