No Spark 50cc from New Member Chris 423 By Bashan (Read 6,868 times)

[Bashan]

This is from Chris423, a new member. Welcome to the forum Chris:

I have a 50cc and cant get spark. I've bought a new coil, CDI. and traced all wires. Im getting fire to the CDI box but not from CDI to coil. I get .9 volts ac from the blue, and 90 volts ac from the red wire from the stator, I checked it at the cdi box There is no power going from the CDI box to the coil. I bought a brand new coil and got a new CDI but still no fire. So i unpluged the black wire with white line wich is the kill wire and still no fire. When I bought it it got fire and I put the coil on then it stoped. Then I moved the scooter it got fire and then it stoped again and hasnt got fire since. Help please, Chris

Chris PM'd me a couple times about his scooter problems so I thought I'd put this on the forum and see what y'all think. I told him to check the trigger voltage which he did and as you can see he got .9v AC. I'm going to go through some diagnostics for him, add something I discovered, and hope y'all can see something I missed.
First of all Chris, here is a diagram of the spark genesis:

Now Chris says he checked the AC power feed to the CDI and got an adequate value. Here's my multimeter testing the red/black on my naked scooter:

A little over a 100v AC, that's right at the top of the scale! This stator has been up and down the pike and just keeps pumping out juice. Chris also checked the trigger wire and got a adequte voltage. here's my blue wire being tested:

.3v AC, more than healthy, it's on steroids! So Chris eliminated those and then said he couldn't get a reading from the CDI feed to the coil. How did you check that Chris? I had always thought that you couldn't get a reading because the power was too intermittant. After some research I found a way to in fact check to see if the CDI is feeding the coil. Set your multimeter to AC voltage and hook the red multimeter probe to the positive coil feed IN SERIES. Put the red probe right into the UNPLUGGED coil wire Then ground the black lead to the coil ground or any close frame ground. Crank the engine and make sure the kill is off:

Well there you go kiddies, 26v AC. This value is supposed to be 5 to 30% of the AC power feed. So since I got 26v AC that lies well within the 5 to 30v AC I should have gotten from the coil feed.

I got this spark tester from Harbor Freight and I thought I'd give it a go just because I bought it. Here it is ready to be plugged and perform it's myriad of diagnostic procedures:

And here it is plugged in with the engine running showing you with the blinking light that the spark plug is firing:

I think I could have figured that out since the scooter was running or I could have held the plug against the valve cover. Well, Chris maybe these guys can help you. But check your blue wire and red wire again. Then check the voltage to the coil. Ohm out your coil according to this diagram:

Then I'd replace my spark plug and check the ground from the engine to the frame. Anybody got any other ideas? Remember, we now have a way to check the votage from the CDI to the coil. Rich

[Alleyoop]

I would check if Grounding it to the FRAME gives a Spark if it does then the GROUND wire from the frame to the engine is bad. Either that or the CDI is bad.
Alleyoop

[sprocket]

Wrong type of CDI.. perhaps you had a DC and have tried to replace it with an AC type?

[Bashan]

Me or him Sprocket? I'm stoked that there's a way to check the power to the coil from an AC CDI, or at least I think there is. That would emininate a lot of guess work when trying to figure these things out. Rich

[sprocket]

Sorry Rich, him.. he switched CDIs.. I think he may have the wrong type... switched DC for AC or visa-versa

[Bashan]

OK, say he's using a DC CDI, my bad. But does that change the fact that i was able to get a reading in AC volts fron the AC CDI to the pos coil connector. That seems to me like it would be a helluva test to see if the CDI was at least sending juice to the coil. Rich

[Alleyoop]

Not a Elecetrical guru but wouldn't you just hook up the multi meter to the positive wire even while on the coil and crank it?
Alleyoop

[Bashan]

That's the method I tried that won't give an accurate reading. By hooking the meter up in paralell apparently there's too erratic of a signal to get a decent reading. Rich

[chris423]

hey guys thanx and sry i havent repled..i have went through 2 more cdis and finally got spark..then i was getting no fuel tryed cleaning the carb and still no fuel..got a new carb and now may be getting too much fuel i have fire plug is wet have checked electronic and mechanical timeing and all is good but still wont start???i am at a complete loss..

[sunlproblems]

check the valves again you may not have tightened up the retaining bolt tight enough