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xr250r bad cdi how do i test it?

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Hello still finding new problems with my new to me old 86 xr250r my newest problem is it randomly loses spark but will return after a while like a day later or so is this a cdi problem like the xr650ls have if not anyone have any other suggestion on what it might be also how do I test a cdi if it is bad? And do any old atv/atc use the same cdi I have a few junk ones laying around I could maybe use thanks for any help in advance.

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Do you have another xr250 of similer age?? or a mate with one?? if so try a swap of the cdi box the problem could also be a faulty coil or ht lead the only way I could think of to test is with a multi meter and check from pin to pin for continuity (separate circuits) coil as well also has the bike been exposed to moisture??? if it has try taking off the coil and cdi box and put them in a LO heated oven to warm them up and evaporate any moisture ?(an old lawn mower trick) see hot you go good luck

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It doesn't seam to matter cold or hot I've rode it for hours no problem actually the two times it has stopped was within 15 min of riding and the first time was when I just got it was trailer home in the rain and now this last time was a day or so after I washed it so maybe something getter wet its been sitting in the garage for five days now and still know spark?

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Unless you pressure washed the bike and shot water directly at the CDI, I doubt washing it is your issue. From what you are saying it may well be simply a bad wire someplace, a bad kill switch or some other intermittent problem. These are often infuriating to track down. Typically, you put a meter on a wire, end to end and work the harness, looking for fluctuations. Try a different kill switch. Being you said it happens hot or cold, I'd go by the manual and do a stator test and a coil test. As vicxr suggested, borrow a known good cdi and try it as well, just to eliminate it as a issue.

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Ok well I think I will start with kill switch and its wiring as two of the times I got it to run agian was taking the switch part and reinstall it nothing seamed to look bad but after I did that it had spark and ran this last time however I took it apart inspected it and put it back on it still didn't work so maybe a break in the wire nearby that reconnected when it got moved around

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14 hours ago, William1 said:

Unless you pressure washed the bike and shot water directly at the CDI, I doubt washing it is your issue. From what you are saying it may well be simply a bad wire someplace, a bad kill switch or some other intermittent problem. These are often infuriating to track down. Typically, you put a meter on a wire, end to end and work the harness, looking for fluctuations. Try a different kill switch. Being you said it happens hot or cold, I'd go by the manual and do a stator test and a coil test. As vicxr suggested, borrow a known good cdi and try it as well, just to eliminate it as a issue.

Exactly right test the loom and as you test each wire give them a wiggle if you have a broken wire the wiggling should find it.  go bit by bit along the wire that will narrow down the point of the brake. cut solder and shrink wrap the wire at the brake. see how you go and good luck:thumbsup:

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I found the problem break in the kill switch line probably best to replace the whole thing wire feels stiff and brittle but for now cut and splice heat shrink around and back on the trail thanks for all the help I am glad it was an easy find.

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