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03-07-2014, 03:09 PM | #1 |
Join Date: Mar 2014
Posts: 13
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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. |
03-07-2014, 08:41 PM | #2 |
Join Date: Jun 2013
Location: Columbus, Ohio
Posts: 50
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check the reg/rectifier
All done in less than 3 pages and countless voltmeter readings
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03-07-2014, 09:27 PM | #4 |
Join Date: Apr 2006
Location: South Haven Michigan
Posts: 225
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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 |
03-07-2014, 10:16 PM | #5 | |
Join Date: Mar 2014
Posts: 13
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03-07-2014, 10:45 PM | #6 | |
Join Date: Apr 2006
Location: South Haven Michigan
Posts: 225
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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.. 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.. 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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03-07-2014, 11:18 PM | #7 | |
Join Date: Mar 2014
Posts: 13
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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.. Last edited by FlyingBlindOnARocket; 03-07-2014 at 11:27 PM. Reason: Addition |
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03-07-2014, 11:27 PM | #8 |
Join Date: Apr 2006
Location: South Haven Michigan
Posts: 225
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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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03-08-2014, 07:27 PM | #9 |
Join Date: Mar 2014
Posts: 13
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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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03-08-2014, 08:37 PM | #10 | |
Join Date: Apr 2006
Location: South Haven Michigan
Posts: 225
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Quote:
http://49ccscoot.proboards.com/threa...park-condtions |
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03-08-2014, 09:04 PM | #11 |
Join Date: Mar 2014
Posts: 13
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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... |
03-08-2014, 09:11 PM | #12 | |
Join Date: Apr 2006
Location: South Haven Michigan
Posts: 225
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03-12-2014, 12:02 PM | #13 |
Join Date: Apr 2006
Location: South Haven Michigan
Posts: 225
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Any luck with your spark issue yet?
Glenn |
03-15-2014, 06:07 PM | #14 |
Join Date: Mar 2014
Posts: 13
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The new trigger coil arrived Friday and I installed it that evening. At first it did produce a spark and would run a bit with some starting fluid, but then I decided that since it had been sitting a while and I had a carb rebuild kit handy, I'd go ahead and use it. So after cleaning it and installing the new part, I put the carb back on and tried nudging it back to life with another shot of starting fluid.
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. |
03-15-2014, 06:37 PM | #15 | |
Join Date: Apr 2006
Location: South Haven Michigan
Posts: 225
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Glenn |
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