Sudden ignition failure of CDI bikes
Sudden ignition failure of CDI bikes Written by
Standard CDI bikes have been known to suddenly stop with no warning and the rider finds there's fuel, but no spark on either side.
The tests to pin down the fault take less time to do than writing this short procedure. If you you new to using multimeters here is a helpful link. Using a Multimeter
Refer to the picture at the bottom of this page for the rest of the instructions.
- First disconnect the kill switch wire and try again Its been known for the weather to get in the contacts under the kill switch knob and this can short ignition power to ground.
No joy? Under the seat are the stator and CDI connectors.
- Open the 2 way connector that carries the blue and white wires.
A quick resistance test between the battery negative terminal (-, NEG, GROUND) and each of these will indicate if the source coils on the stator are OK. Never mind the others for now.
- Quickest test is to measure between the the blue and ground and expect 500 ohms plus the slightly longer but more informative test is to check for 387-473 ohms on the white to ground and 77-95 ohms between white and blue.
Most people know this test by now, its the next bit that seem to go unheeded.
If the stator tests out OK, then its probably producing power for the ignition system and you need to see if the CDI box is handling this power correctly. The tests in the manual require specific meters few if any will have and are a long winded PITA anyway which tells us very lttle we can do anything about.
- There's a quick and dirty test you can do with a cheap common as muck digital meter to see if the CDI is healthy.
I've done it many times to diagnose CDI failures quickly. Basically you need to measure the 'open circuit' DC voltage on the LT wires to the coils 'open circuit' means the wires are disconnected from the coils. Unless its an auto ranging meter, you will need to set the voltage range to 0-250V DC
- DC OK?
With the black probe clamped to battery neg and the red probe stuffed in an opened Coil wire bullet connector, crank the engine on the starter button for a few seconds noting the display then do the other side.
On a well running bike I'd see around 150V perhaps more. On bikes with failed CDIs I've seen as low as 6v. Often both sides, sometimes one when one side has failed.
You will not get a steady reading! The meter is trying to read pulses, most aren't designed for that so dont worry if it flickers about. Just test long enough to get a good indication/average of the output voltage.
If you don't get voltages well up in the 150VDC range, the CDI has likely failed and the options are:
1. Repair: If you are into electronics and have the patience to dig it out the potting compound.
2. Replacement: But new ones are NLA and a 2nd hand one is a crap shoot.
3. Upgrade: get an Ignitech. There are group buys held every now and then for these ignition controls. Check the [and Buying Forum] .
BTW I don't see why the DC output test couldn't be used to test a suspect Ignitech.
Also, a kill switch leaking to ground will easily shut down an Ignitech as its just monitoring a voltage level on a pin.
- And here is the often used stator resistance chart:
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