Help, KX250 won't spark

theckeler · Mar 22, 2009

Need help with my 95 KX250 can't get a spark out of her... I pulled the plug and replaced it with a new one and get no spark. I pulled apart the wiring to the stator and CDI, checked the stator's resistance and it all was fine per the manual. The CDI... I couldn't figure out if I was getting correct results but they all gave me numbers. The coil I checked the primary winding and it fluctuated all over I double checked it with a coil I know that works (from my KDX) and that one too, fluctuated. The secondary showed up fine (did not fluctuate). Not sure if I'm connecting my meter to the right things... I'm using a Craftsman Multimeter (click for image) set to the first click to the right on auto. This is the first time I've really dealt with electrical so I'm not sure if I have it set correctly and if I'm putting it on the right terminals. Anyone give me some help on getting this figured out? Thanks!

jaguar · Mar 23, 2009

figuring it out

I'm an electronics technician. Can your meter read AC voltage? If so, then disconnect the stator wires from the CDI and read the voltage coming from the stator coil when you turn the engine over quickly with your hand or foot on the kickstarter with the spark plug removed (so there's no compression). If it's over 50 volts then the stator coil is probably good.
If good, then reconnect it to the CDI and disconnect the CDI wire from the spark coil. Set the voltmeter on DC volts (around 50 volts max) and connect the positive red lead of the meter to the frame. Connect the black lead of the meter to the wire from the CDI. The meter should jump a bit when cranking the engine because the CDI should output the voltage from the stator, but this output should be just one quick spike of voltage just a fraction of a second long. Some meters probably won't even move their needle. Digital meters definitely won't show anything. You could probably put your pinkie finger on the frame while holding the CDI's output wire between your thumb and first finger and feel for the voltage spike. If there is some output then the CDI is working. When they go bad they don't output anything at all. So if its good then all that is left is the spark coil.

theckeler · Mar 23, 2009

Thanks I'll give it all a try!... I have a digital meter.

jaguar · Mar 23, 2009

Go to Radio Shack and buy their $10 analog (non-digital) meter. Let me know your results

theckeler · Mar 23, 2009

jaguar said:
Go to Radio Shack and buy their $10 analog (non-digital) meter. Let me know your results

I can't use this one to check the first 2 things? I can just put my finger on the third thing, low on the cash right now ha...

If not I'll grab one in a few weeks.

jaguar · Mar 23, 2009

The digital meter can only be used to test the stator output, not the CDI output.

theckeler · Mar 23, 2009

ahhhhhh ok thanks for the info!

jaguar · Mar 23, 2009

Test the CDI output with your hand and write me if you live through it. ha! I'm just kidding. 50 volts for a hundredth of a second is nothing.

theckeler · Mar 26, 2009

Found a new NOS coil for $30, snagged it... hopefully that is the problem. going to snag a tester this weekend and will let you know what I get.

GarbatyA4 · Mar 26, 2009

Clean your grounds.

theckeler · Mar 26, 2009

ya noticed quite a bit of rust where the coil mounts to the frame. I was wondering if those posts on the coil ground to the frame. Asked a buddy who sort-of knows bikes and he said he didn't think they did. But, I'll take some paper to em and a wirebrush when I put on the new one.

GarbatyA4 · Mar 27, 2009

let us know how it goes

jsantapau · Mar 27, 2009

if you have not already done so

unplug your kill switch,and see if you have spark then , if so buy a new kill switch.
Often times it is one of the first things at the scene of a crash,or setting in water and mud when you lay the bike down, the first thing to get rained on or washed and often times the first thing overlooked. Most bikes are wired so that the kill switch is normally opened and when you push it it will connect to ground killing your spark, if there is a short in you switch ...... by disconnecting it you can eliminate it easily and cheaply(free)

also spark plug boot to coil wire are often threaded on for its connection as many times as the boot is pulled off to change a plug this area gets weak, give it a turn clockwise, if it moves and you have a spark again easy and cheap

and yes the coil should be grounded to the frame

do each step separate and you isolate the weak spot

theckeler · Mar 28, 2009

jsantapau said:
if you have not already done so

unplug your kill switch,and see if you have spark then , if so buy a new kill switch.
Often times it is one of the first things at the scene of a crash,or setting in water and mud when you lay the bike down, the first thing to get rained on or washed and often times the first thing overlooked. Most bikes are wired so that the kill switch is normally opened and when you push it it will connect to ground killing your spark, if there is a short in you switch ...... by disconnecting it you can eliminate it easily and cheaply(free)

also spark plug boot to coil wire are often threaded on for its connection as many times as the boot is pulled off to change a plug this area gets weak, give it a turn clockwise, if it moves and you have a spark again easy and cheap

and yes the coil should be grounded to the frame

do each step separate and you isolate the weak spot

New Coil came today... gonna slap it on tomorrow. There is rust where it connects to the frame, I should sand that down a little correct? If it's not sparking after, going to grab non-digital meter and check it all. I did notice that not too many wires where inside the area where the boot connects, compared to the one I just got so...

The kill switch was messed up so it was removed right away and still had no spark.

theckeler · Mar 29, 2009

Thanks everyone for their help, put in the new coil and sparked right up. 2nd kick and it was running.

GarbatyA4 · Mar 30, 2009

What colour was the spark before hand... orange-ish?

What's the colour now with the new coil? white/blue-ish?

Thats how i usually tell if the coil is on its way out.

theckeler · Mar 30, 2009

I never saw the old, I just purchased it. He got it to start when I looked at it, stored it in the garage for couple months and then no spark. The new one is bluish. Glad I got er fixed, thanks everyone for their help!

jesse_54 · Mar 30, 2009

What makes you think the output voltage would be ac? I'm almost positive it would be dc, and your multimeter isn't going to get a reading if you're on the wrong setting.

Help, KX250 won't spark

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