no spark - ac cdi system

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  #1  
Old 11-19-15, 08:44 AM
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no spark - ac cdi system

Hi everyone,
Working on a Roketa 150 scooter. I replaced the guy's starter and started it 3 or 4 times, started right up every time. Called him to come get it and when he arrived it wouldn't start. No spark. I unplugged the black/white wire from the cdi box and still no spark. I get good ground on the green wire. I measure around 50 ac volts from the stator on the black/red wire WITH THE CDI UNPLUGGED. When I plug in the CDI ac voltage drops to around .8 from the stator. I get around .7 ac volts on the blue trigger wire from the stator. Suspecting a CDI problem I replaced it. Same issue. I replaced it with another new one, different brand, same issue.
As I understand it, when I remove the black/white wire from the cdi connection and still get no spark I have narrowed the problem down to an ignition problem i.e. stator, cdi, coil, plug. I doubt all 3 cdi boxes I have here are bad. CDI connector is getting 'enough' ac voltage until I plug it in so the stator is producing voltage. It has to be between the stator and CDI right? Any ideas?
 
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  #2  
Old 11-19-15, 10:17 AM
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That leaves the coil and the pickup sensor. Both can be checked with an ohmmeter for open circuit.
 
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Old 11-19-15, 10:58 AM
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Tested the coil, .5 ohm across the primary and 2.8k ohms across the secondary. Those numbers jive with when it was running (notes from last time I worked on it). Pickup is getting .7 ac volts no matter if the plug is plugged in or not. 140 ohms on pickup wire to ground unplugged.
 
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Old 11-20-15, 08:13 AM
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You said you have good ground on the green wire...IIRC the green wire is the kill wire. Disconnect and see if you get spark.
 
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Old 11-20-15, 08:18 AM
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I'll give it a shot but if I research right the green is the ground for the cdi circuit, the black/white is the kill wire circuit. (black/red is power to cdi and blue (which changes to red/white on this one) is the cdi trigger from stator) I'll report any changes, otherwise I will be outside scratching my head.
 
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Old 11-20-15, 08:56 AM
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Greens are all grounds.

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(from the scooter doc)
 
  #7  
Old 11-20-15, 11:22 AM
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Well,I went out and ran some new wires as follows: (the above diagram is how this is wired by the way)
red black from stator straight to cdi connection
black/white left unplugged
green dedicated ground
blue pickup straight to cdi
basically I removed the factory harness from the equation, took the wiring harness out of the list of variables. I get the same results. That 50volts ac is a little low(?) could the stator be crapping out under load? I'm just throwing things out there because right now I'm lost. The stator is the only thing left
 
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Old 11-20-15, 07:31 PM
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I know basically how the systems work but not the voltages required. It looks like the stator is a three phase unit. Is that correct ?

I'm curious what voltages you get out of the other legs.

Do you have the actual manual for the scooter ?
There are many listed on the site but you didn't post your full name/model number.
 
  #9  
Old 11-21-15, 06:30 AM
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That is kind like me, I know enough to generally get by. From what I gather anything above 20volts ac with a trigger over .5 volts ac will charge the cdi and send power to the coil. I have those requirements until I plug in the CDI. It is a 2008 Roketa MC 68a 150 with engine 1P57QMJ
I was beginning to pull the flywheel to look at the stator but will put it back together enough to check the other voltages when I get some time today. No, I don't have an actual manual, just going off research and theory really. I was reading on a Chinese scooter forum in the UK about no spark diagnosis and one guy seemed to know his stuff. His basic process was provide ground to the green wire on the cdi, remove the black/white wire and see if you get spark. If you get spark you have a safety or switch problem. If you don't you have an ignition component problem. He went on to describe the same condition I have where plugging in the power wire results in drastically reduced ac voltage but never expanded on why or what the cause was. I tried to join that board but they are closed and I have no way of contacting him. How frustrating to find my exact problem in one spot with no way to find the answer.
edit- I went out and checked the voltages put off by the green, white and yellow wires from the stator. The yellow wire had 1.4 ac volts, the white wire had 7 ac volts and the green of course was around .07 volts ac.
 

Last edited by duigoose; 11-21-15 at 06:42 AM. Reason: add info
  #10  
Old 11-22-15, 12:40 PM
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Well, took all of my CDI boxes to another scooter and they all spark. Waiting on a puller so I can look at the stator. Doesn't make sense but that is all that is left
 
  #11  
Old 11-23-15, 06:54 AM
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How frustrating to find my exact problem in one spot with no way to find the answer.
There is a very good forum in the US for help with these Chinese vehicles.
BuggyNews

Over the years there have been dozens of discussions about AC & DC CDI performance/troubleshooting/upgrades. The forum is aimed at 4-wheel buggies, but the 150cc powerplant & electronics is the same as scooters.
 
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