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Yamaha DT125LC MK2/3 CDI Issues!


James Jeremy
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Hello all, im pulling my hair out over my D Reg DT125LC (1986). I bought this a year or so ago for my little bro so he can come out with me when I go green laning.... It was working fine then all of a sudden had an intermittent fault where if would 'race' and basically fart about... Took it to my local mechanic who said it was the main seals and bearings gone and drawing in air so paid loads to have the engine fully rebuilt with new bearing, conrod, piston, etc... Worked fine for a quick ride but then started again... Took it back to him as and we were stripping it I touched the CDI area and it all started to work fine.

Im pretty sure that is not a cable/loom as I can mimic the fault by holding the wires up to the CDI and then move just the CDI and it starts or stops (strangely works when I squeeze the CDI unit).

Anyhow, anyone got any advice? Ive been looking on ebay but cannot find one of these anywhere (hens teeth are more common i've heard).. Does anyone know if any other bikes of the era are compatible (I bought one for a DTR but no luck) or if I can have one made up for me, or this one repaired (or could I do it?!?!?!)....

Really appreciate any help and advice.... cheers ;-)

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Hi Jeremy. I have a 1986 DT125LC mk3. I am also having CDI problems in the sense that so far i cannot get a spark. I managed to pick up another CDI from ebay a while back but have had other projects recently so havnt checked. I may be going to a place soon that can test them so ill get both tested and if they both work and i dont need one, ill keep you in mind. (if you havnt resolved the problem by then).

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Would really really appreciate that Andy... Took to trying to cut into mine tonight (that sealant is nion impossible to get off!) assumed there was only one circuit board enclosed and ended up nicking the smaller one so pretty sure this one will not work at all now, so really need a solution! ;-) I see you live south UK, if you got a dual bike and are interested in some green laning let me know... my site showing byways in Kent & Sussex = www.southerntrails.co.uk .....

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  • 10 years later...

This is really helpful as I have been stumped for months, with sporadic run great then run rough,, hardly run at all rough, and run okay rough, and cannot start rough, followed by runs great.. not always in any particular order of sequence.

 

. mutliple carby rebuilds, diagnosis on pickup coil, and added heat to that and cdi. changed spark plugs spark plug cap , ignition coil... cleaned connectors..

 

I have same issue. finally looking for help online and found your post.

Now convinced after reading your experience that this appears yes to be the CDI...

 

reading elswhere, cdi fault is endemic to the 125LC

 

Michael. 

 

 

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  • 3 months later...
  • 3 months later...

Negotiator, did you change with a new CDI or old one???, as i think this cdi may have an endemic problem??

So if this helps anyone a standard dt125 cdi (one less lead no red and black wire) does not seem to work on a straight swap,,, although all other colours match. Thats a bit strange as the red and black only gives the ignition off signal from what I can gather on an ohm test. With the oem cdi though if you disconnect this red and black cable (which is missing from a standard dt cdi) the bike will  give no spark. The red and black wire  seems to be open circuit for the ignition,,, but in open position of ignition cdi will not spark...  At this stage I am thinking the irregular good run bad run no run runs great is probably cdi sporadic... One guy on youtube hits the cdi then it runs bad or runs good,,, this could be internal solder points,,, so am thinking that may be it at this stage, and will test this accordingly..

he swaps out to a 2rh-mo and changes the leads

 

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