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1984 Yamaha XT 250 died - help diagnose please

  • glennizen
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1984 Yamaha XT 250 died - help diagnose please

Hello everybody,

I recently bought a 1984 Yamaha XT 250. It ran fairly well for about a month. But on a 100 mile round trip in light rain something strange happened and I would like some guidance on what it might be if anyone knows.

The battery that came with the bike does not hold a very good charge but it had been an issue until now. What happened is that while his writing I noticed that my – light indicator for the high beams was not lit and when I came to a stop at a stoplight I looked around at my other lights including my taillight notice that they were out only the head light was on and it was dim. Then not too long after while I was on the highway it started cutting out real bad and then it just died and I had to coast to stop and push it off the highway.

I tried for the better part of an hour to get it to start but I cannot get a spark from it does anyone have any ideas what went wrong? CDI? Ignition control unit? Coil?
26 Sep 2020 08:27 #1

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  • apex
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Based on your description you have a charging system problem. The CDI is powered by the battery, and as you were riding the battery was not being replenished by the charging system and the battery's voltage was used up to the point that the CDI became inoperative (and lights dim, etc...).

Best to get a shop manual and start some testing (unfortunately the Tech Library here does not have a manual uploaded for your bike). You could have electrical connection issues, or needs a component, and you're better off testing to find the problem than just replacing parts.
Allrighty Then
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Last edit: 26 Sep 2020 14:12 by apex.
26 Sep 2020 14:11 #2

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I don't remember the XT250 having a battery powered CDI? Not sure about that though. If it is a battery CDI then charging or replacing the battery will restore the spark.

What they did have was a complicated "safety circuit" that kills the spark if you put the bike in gear with the kick stand down it kills spark... I don't remember the details but it does use the neutral light circuit and I vaguely remember the system could be problematic. We had to bypass the kick stand switch out on the trail on a buddies bike once because it started missing and then lost spark. If neutral light burns out it can cause a problem too.... if battery went dead then you might not get spark unless kick stand switch is bypassed or stand is up?
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
26 Sep 2020 14:48 #3

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Ok, hate to go the other way, but the pic i found for an "84 XT250L shows a separate source coil for the ignition. But--maybe there's different systems for different markets. I dare say to prove a point re battery cdi/tci just recharge the battery & if she runs then it more or less proves i'm wrong. Wasn't uncommon for the earlier style XT to have a faulty source coil. What you say about lights fading until it stopped 'does' point to my idea being wrong. Pic i found will come up small so save it & expand it. Odd color coil is the cdi source coil. I'll keep looking at Babbits diagrams.
26 Sep 2020 15:03 #4

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even the second model on Babbits still shows a cdi source coil so "if i'm right" maybe you have two problems 'as in' charging/lighting 'and' cdi source problems. Getting too complicated for me lol but goodluck. ps, there's a trigger coil involved as well that i'm forgetting. All pretty unlikely unless it was misfiring & getting wrse untill it stopped--which is different to lighting & charging unless battery powered ignition which it doesn't look like at the moment.
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Last edit: 26 Sep 2020 15:13 by RT325.
26 Sep 2020 15:08 #5

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