No spark - Voltage at Sparkplug?

[shnieky]

Hi All,

I have an 1981 XS 650 that while riding this summer stopped running suddenly midride. At the time, I'd tested it and confirmed that I was getting no spark when grounding the plugs to the engine. I'm finally getting around to trying to fix it.

Not sure if these details matter but im including them just in case - the XS has electronic ignition and has the permanent magnet charging system from Tcbros installed. Its been converted to kickstart only. Im using a 3.3 Ohm - Dual Output Coil.

I used my multimeter/test light to try and figure out where the problem was, it looked like i was getting power up to the reg/rectifier when kickstarting it. Replaced the reg/rect and spark plugs and was able to get power to the coil and plug ends. I tested the voltage at the plugs and I was getting 2.8 volts. Should I be getting 12V at the plugs too?

Does this sound like a bad coil/spark plug cables/plugs? Would appreciate any other tests I can do to isolate what could be potentially causing it to not spark.

Thank you!

 

[xjwmx]

It would be interesting to see if you measure anything less than infinite resistance between a coil input and a plug, because of the 2.8V. For dual output coil we usually use used Honda MP08 coils from ebay. They're cheap enough just to try. Be sure to get one that comes with the caps that hold the wires in

 

[Jim]

I tested the voltage at the plugs and I was getting 2.8 volts. Should I be getting 12V at the plugs too?

No, you should be getting upwards of 15,000v at the plugs.... though damned if I know how you'd measure it.
I'm assuming by "kick only" you mean a capacitor has replaced the battery?

 

[Jan_P]

My first thought is a too old weak battery
Charged ???
And please check the fuse holder so the fuse is sitting right
Please report battery status and links to the charging and ignition ( if not Stock )

 

[arcticXS]

No, you should be getting upwards of 15,000v at the plugs.... though damned if I know how you'd measure it.
I'm assuming by "kick only" you mean a capacitor has replaced the battery?

An ignition tester should verify whether the secondary voltage is sufficient. (actually just an enclosed spark gap with a window, and 2 leads, to connect between plug cap and ground) is a common tool for small engine shops, like chainsaws etc)

https://www.amazon.com/Husqvarna-Ignition-Tester-Part-501976401/dp/B00TD5B0QG

 

[mike in idaho]

With the key switch on, is there 12 volts at the battery + primary connection? If so, unplug the other wire and touch it ground, does that create a spark at the plug gap? No spark, check the coil & battery lead connection farther. If you do get spark, check out your electronic ignition setup.

 

[xjwmx]

^To be clearer maybe, ground the other side of the coil primary very briefly and remove the ground to make a spark. Something like a glancing blow since the coil will fry if you do something like just clip it onto a ground

 

[gggGary]

To be "precise" the spark occurs when you remove the wire from the ground.
not running or powered, with an ohm meter plug cap to plug cap should read about 15K ohms.
With caps off spark wire to spark wire about 5K ohms.
Across the two primary terminals on the coil about 3 ohms.
For testing it really helps to power the coil with a 12 volt battery instead of relying on the PMA for juice.