jonapple
Scoot Junior
it is either glory or decline
Posts: 12 
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Post by jonapple on Jul 25, 2015 15:26:18 GMT -5
My Baja 50 suddenly won't startup out of no where. The engine cranks but won't start. I've checked the fuel by the battery and it's fine. I've tested the spark plug and it is still good.
Anybody have any idea what I should troubleshoot next?
I was thinking it could be the CDI. But how do I test that?
Thanks
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Post by Availien on Jul 25, 2015 15:34:02 GMT -5
Take the spark plug out of the engine and hook it back into the cable. Lay it down somewhere you can see the prong and "start" the scooter. This way you can see if it's getting spark. I would do this at night because it's easier to see. If you aren't getting spark then I would try to get another CDI from a scooter that IS running and try that.
What do you mean when you said you tested the spark plug?
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jonapple
Scoot Junior
it is either glory or decline
Posts: 12
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Post by jonapple on Jul 25, 2015 16:32:04 GMT -5
Hey thanks for the quick reply.
Sorry let me clarified my issue.
My baja 50 engine cranks but won't start. I checked the fuel and its still good. So I took the spark plug out of the engine. Hook it to that cable. And touch it with one of the grounded nut and turn the engine. I don't see any sparks coming out of it.
So I took that spark plug out and put it in my other scooter and and tested it. This time I see sparks. So this concluded that the spark plug is still good.
Unfortunately my 'mechanical know how' stops here : ]
I don't know what to check for next. I'm suspecting it is the CDI. I tried to swapped CDI but they seemed to be two different CDI. CDI on my baja 50 is smaller than the one on my znen 150.
What now guys?
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Post by Availien on Jul 25, 2015 18:16:53 GMT -5
I would see if I could get a buddy with a running 50cc to let you borrow their CDI for a few seconds. Do you know if the battery is still good? DC fired bikes require a good battery to run. AC fired runs off of the flywheel/stator and require no battery at all.
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Post by Availien on Jul 25, 2015 18:22:37 GMT -5
Here is an excerpt from Scrappydogscooters.com about the differences between AC/DC CDI's:
AC vs DC fired or pulsed CDI IGNITION SYSTEMS
Hey MO! What's all this I hear about AC and DC fired or pulsed CDI'S? - Harried in Henderson
Ok first the short answer.
Here is the readers digest of how a CDI works
In all cases there is a magnet that passes a magnetic coil and induces a pulse in that coil which then is wired to the CDI and causes the small induced pulse to fire an electronic device (there are more than 1 type but this all happens inside the CDI) Which discharges the larger pulse stored in a capacitor. This larger output pulse is wired to the coil where the large pulse is able to make the coil function as a voltage increasing transformer thereby producing the very high voltage necessary to create a spark across the gap of the spark plug.
Now for the 2 main type of CDI used in the 49 cc scooter market, AC and DC Both function essentially the same. With the AC unit, alternating plus and minus varying voltages are used to charge the capacitor described in the paragraph above. The DC unit takes 12 volts more or less DC from the battery and that voltage is used to charge the capacitor described in the paragraph above.
Pros and Cons:
AC unit allows the engine to run without the need for a battery or charging system of any kind.
DC unit was created to allow higher RPM ranges due to the instantaneous availability of the Charging current. Where the AC one has lots of complex and difficult to explain things like coil flux density and residual decay etc.
The wiring is different also usually but not always, the ac ones have a rectifier or diode ahead of the CDI and the DC ones just connect directly to the battery.
the way to tell for sure is to turn on the key and see if 12v is present at the CDI assuming all else is correct. Some units that are DC include:
Kymco Agility 50, Diamo Velocity, Vento Triton, Schwinn, Tomos, and other high end Chinese, Korean, and Taiwanese scooters.
One easy way to tell is the size of your CDI unit. The AC fired CDI will be much smaller than the DC fired CDI, as shown in this picture. Also, you have two plugs on the CDI, one with four, the other two. If the two wire plug actually has only one wire in it, it's a DC. If it has two wires in it, it is an AC fired. The number of wires is only a loose guide. The size of the box, along with this guide is a better determination. An AC box will be smaller (see pic) and will measure about 1 1/2 by 2 1/2 approximately, the DC box will be much larger as it has a DC-DC converter in it. Such words as AC or DC pulsed or AC or DC triggered are the same thing as the AC or DC fired units. One quick warning on performance units, with the advanced angle of our CDI's your engine may actually run worse if it's not running right or is carbureted too lean. I'd recommend installing a larger main jet to take full advantage of these units.
Here is somewhat simplified checklist to determine type:
Headlights turn on with key, DC. Headlights turn on with engine,AC
Engine does not run without batter, DC. Engine runs without battery, AC
CDI box is pretty large, DC. CDI box is smaller, AC (note: our new digital DC units are smaller)
There is one wire on the two part plug, DC. There is two wires on the two part plug, DC.
Hope this helps. MO!
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jonapple
Scoot Junior
it is either glory or decline
Posts: 12
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Post by jonapple on Jul 26, 2015 1:55:15 GMT -5
I think my Baja sc50 is a AC. I've tried kick started it before and it work. And yes the battery is good. It just doesn't give sparks ATM. Maybe I'm gonna replace the CDI.
You guys know where I can get a CDI for my 2008 baja sc50?
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Post by Availien on Jul 26, 2015 8:43:26 GMT -5
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Post by Availien on Jul 26, 2015 8:45:12 GMT -5
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jonapple
Scoot Junior
it is either glory or decline
Posts: 12
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Post by jonapple on Jul 26, 2015 12:25:43 GMT -5
Hey Avalien. Thank you so much for all the information. I've email the eBay seller with the racing proformance CDI to make sure that CDI will work for my baja 50.
I'll update you guys the result after I replaced the CDI.
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Post by Availien on Jul 26, 2015 12:40:30 GMT -5
Honestly, a stock CDI will probably work just as good. A timing modification can result in much better advancing than a so called "racing CDI". The only reason I bought one was to make sure I wasn't restricted by a rev limiter. Plus they look cool.
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Post by 90GTVert on Jul 26, 2015 15:08:39 GMT -5
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