‘85 250sx no spark

[MikeD70]

i was thinkin it might be possible theres bad wiring if the reading is still high at the cdi plug but normal at the coil

New coil measured .06 at CDI plug, not sure if this should be in spec since it is an aftermarket coil and not an oem one.
Is it possible the exciter is not putting out correctly even though the resistance measured in spec. Can the voltage out be measured for the exciter, if so what value should I expect?

[lndy650]

im not sure how much voltage the exciter coil would produce at the rpms of the engine being cranked over but at high rpm i think its somewhere around 100.
ok so the exciter puts out ac voltage to the cdi so technically you could test for any ac voltage coming out of the exciter. if you get a reading then test the wire that sends that voltage to the coil and if theres no reading you know its the cdi and if there is then its the coil. anyway seeing the cdi is off a running bike we know that should be good.
I did have this arctic cat f1000 once that had a bad computer but replacing it resulted in a second of spark then nothing. turns out even though the ohms reading was ok the exciter coil was producing too much voltage and burned out the computer. i ended up having to buy another computer and a new stator which together at our dealer cost was almost a g note.

ill look more into the rated output of the exciter coil and you test it at crank rpm with your meter on ac volts and see what you come up with.
as far as the coil reading your right .06 might be ok for that coil. is the reading at the coil .06?

[gimmeamidget]

He posted a youtube video of him testing at the coil in AC volts and it appeared the voltage was only there part of the time but I am wondering if the meter cant read fast enough to keep up with the on/off volts. I always just used a cheap tester light and it flashed as I would expect a spark at the plug. I did see volts which I think should have been amped up at the coil and produce a spark....maybe not correct but some sort of spark.

[gimmeamidget]

I would try pulling off the cap on the OEM coil and cutting 1/4" off the wire and replacing the cap to ensure a good connection and rechecking resistance. I like OEM to cheap stuff.

[lndy650]

yes the video he did was the external coil and you wouldnt have constant voltage you would only have voltage when the cdi tells it to send a spark so ya its gonna look screwy on a meter especially set to auto-range. the test light is worth trying if he has one.(if not they are a couple bucks) Im pretty sure i already had him test the plug wire on the old coil and it was good but that is a good idea to cut the wire back a little and your idea to use the old coil now that he has a cdi from a running atc is also a good idea couldn't hurt to try.
im asking him to test the voltage out of the exciter coil(internal stator coil) because i think we should try starting from the source of the ignition and work our way up.