Hello
I'm a student technician (intern) trying to repair my sym scooter, mio 100cc. I am having trouble with the ignition. My scooter lost power on the way while I was driving. Having checked fuel, oil and proper air flow, the next thing I checked was for spark and I was not getting anything. My air flow is fine, cleaned the carberato and checked if my carberato is getting fuel which tested fine. I measured for a shot circuit of which I did not find any. So I changed the CDI unit, and still on the new one I'm getting the same result. I then tested the coil unit and spark plug externally using a 35V DC supply and triggering the input to coil which would have been from CDI unit by single quick tapping using the 35V. Then I got a good spark. This suggested to me the coil and spark plug are fine.

When turning the engine over with the coil depending on CDI I do not get a spark. I am thinking it is the input from trigger pickup module that is not working which in turn is not triggering the CDI to fire and the spark is not discharged. I measured this input to be 0.7V using a fluke meter.

My CDI is a 6 pin device ( 4 by 2) pin layout.
~ pin 1 is my input from trigger pickup module [I measured 0.7V when turning the engine]
~pin 2 is the ignition coil positive
~pin 3 is ground (tested fine)
~ pin 4 also ground (test fine)
~ pin 5 is a 12V DC power (ignition switch). Measuring from this pin to positive terminal of the battery, it measures 12V. But once the switch is turned On it measures 0V. This is correct according to circuit diagram I'm using for the connection of 150cc GY6 CDI pin layout as the ignition normally open switch pulls the pin 5 to ground when turned On.
~pin 6 is the 12V DC power always present.
12V DC power is present on pin 6.

I have tried everything I can think of. May you please assist me on where the problem is. How do I test if my 0.7V from pick up is sufficient for triggering the CDI to output the ignition cool so that it my fire the spark plug? I checked for my timing, it looks alright and well aligned but I'm still not getting the correct pickup input if I'm correct. Please assist me.

 

This is correct according to circuit diagram I'm using for the connection of 150cc GY6 CDI pin layout as the ignition normally open switch pulls the pin 5 to ground when turned On.

Is this the actual CDI your using on the scooter? Or just the one you wound a schematic for?

Have you measured the output from the 'trigger' when rotating the flywheel by hand? Have you checked for continuity on the wire between the trigger and the CDI? Or for that matter all of the wires involved with the CDI.

 

Is this the actual CDI your using on the scooter? Or just the one you wound a schematic for?

Have you measured the output from the 'trigger' when rotating the flywheel by hand? Have you checked for continuity on the wire between the trigger and the CDI? Or for that matter all of the wires involved with the CDI.

Shortbus is correct in that the very first thing to check is all of the connections. The trigger circuit is a very low power area and so it is very important to check for both open circuits and short circuits across the signal path. Unfortunately, the practice of replacing parts, starting with the most expensive ones, is seldom a best option. Of course, it really helps to have a circuit diagram and a description of how a system is supposed to work.

 

Sounds like the Kill Switch is grounded to kill the engine, here is a circuit diagram for your AC version.

 

Sounds like the Kill Switch is grounded to kill the engine, here is a circuit diagram for your AC version.


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The AC version most likely has a winding on the stator for around 350V - failure there isn't exactly rare.