YZ 250 doesnt wanna run!!!

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KDXrider1989
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Re: YZ 250 doesnt wanna run!!!

Post by KDXrider1989 »

Magneto/source coil checks in perfectly, the ignition coil is a different story. Primary resistance limits are 0.20-0.30 ohms, secondary resistance limits are 40k-48k ohms. My coil checked in at 0.5 ohms and 3.84k ohms, respectively. more resistance on primary, a lot less resistance on secondary

shows a good spark when I roll the engine over on a good kick though, perhaps I should still replace it or figure out a way to fix this
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Re: YZ 250 doesnt wanna run!!!

Post by John_S »

Every coil I've ever tested new or not checks in at least .5 ohms. I wonder if that 3.84K would show as 38,400K on another setting. Keep in mind I suck with electrical and have to flip that dial all over the different ohm settings before I get it right.
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Re: YZ 250 doesnt wanna run!!!

Post by KDXrider1989 »

John_S wrote:Every coil I've ever tested new or not checks in at least .5 ohms. I wonder if that 3.84K would show as 38,400K on another setting. Keep in mind I suck with electrical and have to flip that dial all over the different ohm settings before I get it right.
me too, but I know its 3.84 k because that shows on a setting that reads up to 20k but wont show on a setting reading up to 2000
KDXrider1989
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Re: YZ 250 doesnt wanna run!!!

Post by KDXrider1989 »

In regards to my previous post, I actually found the same exact coil for this bike on eBay that came off a running machine. Primary resistance 0.8 ohms, secondary resistance 3.6k ohms. Very similar to mine
Dekon
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YZ 250 doesnt wanna run!!!

Post by Dekon »

The manual says to set the ohmmeter R X 100 for the pickup and charge coils.

For the ignition coil primary resistance, set on ohms X 1, measure between both coil primary terminals.

For the ignition coil secondary resistance, set on ohms X 100, measure between either primary lead and the high voltage cable.
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YZ 250 doesnt wanna run!!!

Post by Dekon »

Any update?
KDXrider1989
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Re: YZ 250 doesnt wanna run!!!

Post by KDXrider1989 »

so the problem was definitely the CDI box, got it swapped out for one off a running bike and it gave out PLENTY of spark, the bike started on the 3rd kick. so it runs now but doesn't have a powerband, either due to timing being off or power valve not operating correctly, Ill investigate this weekend

on the flip side, I attempted to dig into my old CDI just to check the circuitry. the baking in the oven trick didn't work on this thing, so I wanted to open it up. needless to say it didn't work out so well, the box is filled with a tough silicone substance that nearly makes it impossible to remove the circuitry without destroying the box itself
KDXrider1989
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Re: YZ 250 doesnt wanna run!!!

Post by KDXrider1989 »

I guess the takeaway from all this is that a CDI box CAN in fact be bad but still create some spark, Ive owned over 30 motorcycles and this is the first time I had to replace a CDI box

special thanks to Dekon for coming through with the ignition specs, no sense in buying an entire manual for just two pages of info
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YZ 250 doesnt wanna run!!!

Post by Dekon »

Glad to see you got it running. Now you to post up some pics of it. A '85 YZ125 was my first bike; so I'm a little partial to '85 Yamahas. I'm working on an '89 YZ125 that I picked up in milk crates and a Tupperware tote. Haven't started to put it together yet, finally got all the parts together for the build. Nothing like the feeling of saving an old bike.
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Re: YZ 250 doesnt wanna run!!!

Post by KDXGarage »

Jason wrote:Have you ever opened a CDI before? :lol:
Congratulations on getting it going.

No need to buy a manual until you need one the next time and someone is not there to spoon feed you. Don't be such a cheapskate. :lol:
Thank you for participating on kdxrider.net. :bravo:
To post pictures from a device: viewtopic.php?f=88&t=24128
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Re: YZ 250 doesnt wanna run!!!

Post by KDXrider1989 »

Image

as previously mentioned, Yamahas are probably my least favorite bikes simply because Ive had bad luck with them, yet this is the 3rd YZ 250 Ive owned, all my other bikes Ive owned at some point were for the most part different models. My other two YZ 250s were an '03 and a '92, and now I have this '85 which will soon be for sale
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Re: YZ 250 doesnt wanna run!!!

Post by KDXGarage »

What is Dekon's cut for helping to get it going? LOL
Thank you for participating on kdxrider.net. :bravo:
To post pictures from a device: viewtopic.php?f=88&t=24128
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