Michael DT125LCIII Posted December 28, 2010 Share Posted December 28, 2010 Hello, I have a 1987 DT 125 LC III that I am just about finished rebuilding. I am getting a spark out of it however it is very weak. I checked the resistance of the Exciter (source) coil and pulser coil as instructed in the manual (haynes) and got a reading of 378 Ohms. The manual says that it should read 180 +/- 10% so between (162-198)ohms. The manual states that if the coil is suspect by this test to remove the stator plate from the machine and take the assembly to a Yamaha dealer for further inspection. Is it possible to test these coils myself? The DT coils can be renewed individually if I can find out which one is faulty, I just don't know how to do this. Or do you have any suggestions as to what else it could be? Does anyone know the steps to test this sort of thing or do I need to bring it in to a dealer as the manual states? If so does anyone have any idea as to how much a dealer might charge for that type of testing and how much coils would cost? Thank you Link to comment Share on other sites More sharing options...
Moderator Airhead Posted December 28, 2010 Moderator Share Posted December 28, 2010 Hello, I have a 1987 DT 125 LC III that I am just about finished rebuilding. I am getting a spark out of it however it is very weak. I checked the resistance of the Exciter (source) coil and pulser coil as instructed in the manual (haynes) and got a reading of 378 Ohms. The manual says that it should read 180 +/- 10% so between (162-198)ohms. The manual states that if the coil is suspect by this test to remove the stator plate from the machine and take the assembly to a Yamaha dealer for further inspection. Is it possible to test these coils myself? The DT coils can be renewed individually if I can find out which one is faulty, I just don't know how to do this. Or do you have any suggestions as to what else it could be? Does anyone know the steps to test this sort of thing or do I need to bring it in to a dealer as the manual states? If so does anyone have any idea as to how much a dealer might charge for that type of testing and how much coils would cost? Thank you 1:51 am yeah Michael its a bugger when you cant sleep because of a weak spark eh? i must admit i was confused for a while as this bike doent actually have a pulser coil does it? The reading is much higher than 180 Ohms as is often the case with dirty or corroded contacts. I assume you checked it via the black and black/red at the loom socket? The black is bolted to the chassis of the stator plate so check you have a dead short from the black at the socket to the stator plate, and then to the coil grounding lug...you should have. Typically the black wire will be screwed to the back of the stator plate and the coils will be grounded to the stator plate via their mounting pillar bolts. Have a look at the pictures here at the top of the first pic you will see how the coils are grounded under the mounting screws and how the black wire is terminated to the back of the stator plate Although they are not pictures of your stator assembly ( DT175MX ) so the final concusive test of the coil would be to check between the black/red wire and the coil grounding lug beneath the mounting screw. ...Paul I expect yours will be similar Link to comment Share on other sites More sharing options...
Michael DT125LCIII Posted December 28, 2010 Author Share Posted December 28, 2010 Hello! Thanks for that quick and thorough response. Ya I was tossing and turning so I decided to post! I was just posting what was in the book. What is a pulser coil anyways? I'll check out those contacts in the next couple days and post what I find. Thanks again! Mike Link to comment Share on other sites More sharing options...
Moderator Airhead Posted December 28, 2010 Moderator Share Posted December 28, 2010 ........... What is a pulser coil anyways? ....... The top picture with the very small coil on it, that's a pulser coil as the flywheel turns it gives the CDI a signal when to discharge its stored energy from its in built capacitor CDI is an acronym for 'Capacitor Discharge Ignition' apparently your bike doesnt have a pulse coil and the CDI is triggered by the strength of the voltage from the source coil Link to comment Share on other sites More sharing options...
Recommended Posts