Weak spark/ loosing spark

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3/3/2017 6:26 PM

Got a 1994 Cr250 have been everywhere with this bike
has weak spark then no spark
kick it a couple of times haves spark
a couple more kicks it has no spark
Test coil primary resistance 0.4
Secondly 11.31k
Tested stator resistance
Exciter resistance 173
Pulse resistance 234
All within spec according to my clymer manual
Even tried two different Muiltmeters
Got 32:1 mixer fuel non ethonal
178-182 psi compression within 2-4 kicks builds that much
Kill switch new (old one broke off anyway) have it completely off bike for testing
Cleaned all engine and frame grounds and ran 10 gauge jumper wire from coil ground on frame under tank to anywhere on bike same results
Any info/leads wpuld be great full

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3/3/2017 7:31 PM
Edited Date/Time: 3/3/2017 7:32 PM

That primary side on the coil seems too low. That would cause the coil to break down and loose spark. In MHO it should read above 16 or so and no less than 12 too be good and not break down.
The secondary side seems a bit high, or at least I think it should be as low as possible to insure that a good hot spark makes it to the plug. This can be caused by a dirty coil mount, bad plug cap connection or corrosion .

Paw Paw

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3/3/2017 7:52 PM

According to my manual primary resistance should be 0.2-0.4 ohms on 93' and newer cr250 and secondary resistance should be 9-16k ohms with spark cap on and 10-16k ohms without cap all tests take above 68 degrees like manual suggests
Have a new NGK replacement cap on and I cleaned ground coil to frame to bare metal with a grinder

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3/3/2017 8:52 PM

Dumb question here...
Have you tried different plugs???
I ask because my son one time said his yz85 wasn't running right. I rode it hard out in the end of the pits and it ran great. He went back on the track and came right back sayin the same thing. I started looking at the bike and was going to change the plug. I pulled the cap off and half of the electrode metal center wire came out in the cap. I guess the cap was keeping it in contact enough that on smooth ground it ran fine. But when you started hiring the bumps on the track , it would separate a little and then go back together causing it to run run like crap on the track.
Just a thought...

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3/4/2017 7:15 AM

tyler 13 wrote:

According to my manual primary resistance should be 0.2-0.4 ohms on 93' and newer cr250 and secondary resistance should be ...more

Yes, I too have seen those same figures before and I have found them to be in error. If the primary side reading were that low the coil would break down under load and or heat. Try a different coil if all else is good as stated or find a good one and checks it's primary ohms readings. I have found that the higher readings on the primary side of the coil will keep it from breaking down from load or heat.
Manuals are great items and I strongly suggest everyone have one for his bike, but with that said I have also found mistakes in them over the years due to translation issues. I think in this case the decimal point in the figure is placed incorrectly.

Paw Paw

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3/4/2017 9:55 AM
Edited Date/Time: 3/4/2017 9:56 AM

I've tried two different NGK BR8EG plugs and the original one I got with bike same results
I bought it not running and rebuilt hole bike then came to this issue
I bought new EMGO coil and same result the bike when kicked over tries 99% of time to start but won't fire
I even rebuilt carb with all new jet/seals with same settings as old ones
The plug is damp after tring 20 times to start which must mean getting fuel and have compression just spark is holding it back
Thanks for any input on this machine so far
I'm sure it'll be running soon enough

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3/4/2017 11:51 AM

Did you replace the crank seals?

Paw Paw

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3/4/2017 12:19 PM

Yea all new seals/gaskets on engine new crank (old one broken pieces) new top end

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3/9/2017 5:27 PM

Update!!!
It's alive and well
Replace stator with electrosport one
runs great lots of spark due to new coil from previous thoughts and new stator
New one tested 87.4 ohms blue/white wire the exciter coil wires
235 ohms blue/yellow and green/white wire the pulse coil wires

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