electrics, electrics, electrics grrrrrrrr

  • Hi All, Im new to the forum and looking for some help..... My son and I bought a DT125R from eBay that had electrical damage to wiring after someone had tried to steal it, mainly all wires ripped off the back of the rev counter and ignition. We reconnected all these (Correctly I have good basic knowledge and can use a meter to test a switch or for continuity) and tested all for continuity including ignition switch, dead mans switch etc, following Haynes manual wiring diagram DT-3RM9, bike actually has loom 3RM20. Anyway with the ignition switch in the off position the bike has a spark !!!!, turning ignition on it sparks once then no spark (the ignition is definitely working on connects red and brown and also connects blue yellow to blue black (kill with is shorted for now.... Mad or what.... most people cant get a spark we get one when we don't want one (by the way bike fully dismantled and not in state to run). I have checked every wire in the loom for continuity so I know these are all OK. The only thing missing from the bike is the read switch and side stand switch, so I am thinking CDI is knackered or could it be something on the charging unit of the stator providing high voltage to the CDI and killing it, by the way I have checked the resistance on the Source and pulser coils and both are OK, I cant find anything that tells me how to check the lightening charging coils (when I check continuity from the 4 way plug that connect to I can see that they have a resistance to earth on the stator plate (all 4 wires)is this correct?.... Any and all ideas are most welcome, Thanks, Simon

  • I've got a feeling the kill switch makes connection, grounding a wire to kill the engine. If you've got the two kill switch wires shorted together, that would be like having the kill switch in 'off' position. Also my dt will spark once or twice with kill switch in off position.

  • Also check the side stand switch, as that will also kill the engine too.

  • Yeah you see this often with the side stand switch and kill switch.

  • Thanks for the replies, just to be clear, it doesn't matter whether I have the side stand open or closed or kill switch open or closed or both open or both closed, with ignition on or off I always get a spark unless I connect the battery up, as soon as battery is connected the spark stops (with ignition on) with battery connected and ignition off I get a spark :-(, by the way I have checked and double checked the ignition switching and its working correctly (I am 100 5 certain, off disconnects all wires).

  • @sward That doesn't make sense to me, are you saying that with no battery connected you get a spark, but when the battery is connected you get no spark? How would your electrics work with nothing to power them? If that's the case then you have a short somewhere and most likely its somewhere along the battery cables.

  • @NINJA Unlike an alternator, the DT uses a generator. Meaning, you don't need power to make power.

    Either way, I know the behaviour of the bike is different when the battery is low. But I've not gone experienced too much myself.

  • @Calum AAAHHH Well that explains it then - thank you. :thumbs_up_light_skin_tone:

  • @Calum the bike will spark just fine with a dead battery you will have no power valve though

  • @declan That's not true, the bike may not fire properly. As is the case with my DTR.

    The generator simply does not make enough power to power the lights, fire the ignition and operate the servo.

  • @Calum may not fire properly but it will always start and run

  • @declan Well, never say always. If there is a heavy enough load on the electrical system then it may struggle to fire. But yes, my bike runs, just really poorly above 5k RPM

  • There is two parts to the generator on a dt and most bikes. There is charging coils that produce Ac current that the regulator/rectifier converts to 12v dc, to charge the battery. The 2nd is ignition coils which are used to produce a spark at the coil. Most bikes will run fine with out a battery, but with out the battery there to 'buffer' the voltage from the reg/rec you run the risk of voltage spikes so not recommended.
    I presume the ignition switch interrupts the main power feed ( red and brown wires) and a feed to the ignition system, through the other two wires. I would see if the bike sparks with these other two wires (blue I think) disconnected at the ignition switch, but with the ignition on.

  • @Calum yeah that’s about right

  • I tracked down the issue to a broken wire in the loom, so all fixed and great to hear the bike running, I'm not going to identify the individual wire that was causing this as if people know they could just cut one wire and steal the bike, though in addition as many people talked about bad earths I also made sure they were all spot too, could have been a combination of two things. lol.

    Thanks for all the suggestions and help,


  • @sward Glad your now sorted, post some pics or a vid of the bike running dude!!! :grinning_face_with_smiling_eyes: :grinning_face_with_smiling_eyes: :grinning_face_with_smiling_eyes: