No spark on 110cc mini atv

[TallGuy]

Originally Posted by LynnEdwards

Is this a picture of your CDI?



If so, set up your quad to run - all kill switches off, tether plug in place, ignition switch on. Then unplug the CDI and use you meter to measure the kill switch pin resistance (in ohms) in the wiring harness to ground. It should read infinite ohms (open circuit). If it reads a very low value of resistance (less than 100 ohms) then you have a kill switch problem. We can go from there.

If you have a different CDI such as a 4 pin version (much less common than the above 5 pin version) then that's a complete different path.

If you don't have a kill switch problem then the next step is to use your meter to measure the power supply voltage to the CDI, the trigger voltage to the CDI, and the resistance of the coil primary to ground. We can go there if necessary.

Kill switch issues (and associated wiring) are the most common causes of no spark and the easiest to fix. That's the place to start. We can branch out from there as needed.

You guys are a wonderful wealth of knowledge, thank you! I'm in the exact same position as the original poster.

I have a Roketa 50cc quad, the same electrical system as this thread. Today I ran down and got another CDI unit, hoping this was the problem, but no luck. Then I found this thread. I did as mentioned, and the kill switches are ruled out.

(EDIT) Forgive my stupidity, tested wrong pins originally. :oops:

The power supply voltage to the CDI, measured when cranking, is around 46 volts, could be more if the battery is fully charged. Timing trigger registers 5.3 volts, and a resistance test on this pin is 0.5 ohms. Ground pin checks ok, kill switch checks ok, and the ignition coil pin shows no voltage.

Any ideas? Thanks!

[TallGuy]

Originally Posted by LynnEdwards

60 volts AC on the ignition power pin is fine.

0.2 volts AC on the trigger wire is on the low side. It really depends on your meter. Since you didn't report something like 0.23 volts AC I'm assuming that your least significant digit on the meter is 0.1 volts on the AC ranges. So it really could be more like 0.1 volts (or 0.3 volts).

The trigger voltage is actually very complicated. It really consists of two closely spaced +/- pulses about 5 volts high (at cranking speeds) followed by long periods of zero volts in between. Volt meters aren't really designed to measure this kind of complex waveform, so there is some variation between meters. Using a meter to measure this is not optimum, but often the only option.

As another data point try measuring the resistance of this pin in the wiring harness to ground (CDI unplugged). You should get around 150 ohms.

Just for informational purposes this is a graphic display of what the voltage should be on that pin:



The relatively long periods of zero volts between pulse pairs is why you read much less than the 5 volt peaks.

The trigger pickup coil is outside the flywheel, but under the engine cover. On some quads the gap between the pickup coil and the flywheel is adjustable. You might want to see if yours is adjustable, and then try narrowing the gap. That will increase your trigger voltage substantially. I have read posts from others who have solved their no spark problem by narrowing this gap.

Also make sure that the connection from the CDI output through the ignition coil primary is OK. Measure the resistance from the Ignition Coil pin in the wiring harness to ground. You should get around 1-2 ohms. You should not get zero ohms.

Measuring resistance on the timing trigger and ignition coil pins on the harness, I get 0.5 ohms on both of them.

[LynnEdwards]

Originally Posted by TallGuy

...The power supply voltage to the CDI, measured when cranking, is around 46 volts, could be more if the battery is fully charged. Timing trigger registers 5.3 volts, and a resistance test on this pin is 0.5 ohms. Ground pin checks ok, kill switch checks ok, and the ignition coil pin shows no voltage....

Two problems:

1) 0.5 ohms on the timing trigger pin is way too low. It should be more like 150 ohms.

2) 5.3 volts AC on the trigger pin is way too high. It should be more like 0.3 to 0.5 volts AC

Down around your stator there is a group of wires that come out of the engine (from the stator) and tie into the wiring harness. Is there any possibility that these may have been miswired recently?

Measure the resistance of all the wires to ground at the stator output connector(s). Do any of them read around 150 ohms?

What I'm wondering is if the battery charge winding in the stator is wired to the trigger input of the CDI. It's resistance and output voltage at cranking speeds is a lot closer to what you measured for the trigger pin then the expected trigger voltage and resistance.

You may want to measure the trigger voltage and resistances again just to be sure you get the same values. And remember that the picture of the CDI pins is mirror imaged from the mating pins in the wiring harness since you have to flip the connector over to look into the pins.

[TallGuy]

As for the measurements, I double checked and still have the same thing.

The 3 wires coming out of the stator, a couple of them are very small in resistance, around 0.5 ohms, the other is around 330 ohms.

As for messing up a wire - it's possible. The 4 wheeler ran fine, then one day it had power issues, so I jiggled the wires around and checked all the connections. Possibility that I got one wrong, I don't know - it's been 6 months since I fixed that issue, and just haven't gotten around to fixing the spark problem. That power problem was at the fuse, just a bad connection.

[TallGuy]

Lynn, I and my kids very much appreciate your help. With your insight, I pulled the stator off and traced where the timing trigger wire was going. Come to find out two of the wires WERE backwards. After moving them to the proper place, I have a spark.

Now to try adjusting the carburetor so I don't have to crank it for 15 minutes in the cool air to start it. I think I'll clean up the wiring too. :wink:

Thank you!

[LynnEdwards]

TallGuy, I'm glad you were able to find the problem.

[bigbadbob17]

first off, this forum has a tonne of great info!!

I purchased a gio 110 mini hummer the other day, I drove it around the yard for probably 10 rides without an issue, parked it by the front door and came inside. Went back out an hour later and it wont start! Tested the CDI, AC ignition power is within range, timing trigger is within range, CDI is grounded, kill switch ruled out but I have 0 volts on the ignition coil wire when I turn the engine over, does this mean a bad CDI??