DT125 - Electrical issues - sparks all the time

[SiWard]

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, when switched on connects red and brown and also connects blue yellow to blue black (kill switch is shorted for now), with battery disconnected has a spark with ignition on and off.... 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 reed 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 the coils I can see that all connections have a resistance to earth on the stator plate (all 4 wires)is this correct?.... Any and all ideas are most welcome as we are completely stuck , Thanks, Simon

[Easy-X]

Has to be a wiring issue. I would have thought that ignition off would route the coil power to ground otherwise what's the point

What year is this BTW?
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[SiWard]

It’s a 2001

[Robby]

Ignition switch, particularly if it's a basic 3-wire one.

All the ignition switch does it dump circuits back to ground in the off position. Ripping the wires out the back does the same job as putting a key in it.

So I would be making sure that the ground wire on the ignition switch is connected to the switch and the loom/frame.

[jaffa90]

"""""Anyway with the ignition switch in the off position the bike has a spark !!!!, """""
So where is the live coming from?
A switch is a switch, usually giving a live feed to the fuse box and circuits.

[SiWard]

Hi All, thank you for your replies the help is very much appreciated - I have attached the wiring diagram for reference - the ignition is circled.
I cant see that it puts anything to ground though for someone like me its a very complicated drawing.
I have checked every wire goes to or connects to where it should go. The only ones I have issues with are the Reed switch which is missing (so wires open ended on either side of this) and the side stand switch which is also missing (I have had this open and closed), the dead mans switch is shorted at the moment.
There is no fuse box, only fuse is on the live from the battery.
Maybe worth mentioning that when I turn the key to the on position the power valve does its reset (which it should do).


What can I check next?

Thanks, Simon

[Nobby the Bastard]

[Easy-X]

Ah well, scratch what I said about grounding the coil. That's a thing for older bikes

I take it item 9 on the diagram is the ECU? Looks like that controls the spark directly... and that "knows" to power up via a live feed from the ignition switch.

I think we're all on the same page with this one
____________________
Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[SiWard]

yes 9 on the diagram is the ECU, when you say we are all on the same page, are you saying you think its probably an ECU / CDI fault?

Its obviously and expensive thing to replace so im open to testing anything else I can before looking for one

Can anyone think of anything else I could look at....

If the reed switch is cut off / missing, is there something I can put in its place ore can I connect the two wires together?

Thanks,

Simon

[Easy-X]

Lol... no I meant there has to be something up with the ignition switch or related wiring

A "reed" switch just describes any magnetically activated switch... its still a switch! So if you have to, wire in a traditional switch for testing or just twist the wires together.

What's this reed switch actually for?
____________________
Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[SiWard]

The read switch is part of a circuit to restrict the bike to a lower performance. it sits in the beck of the speedo usually, people move it away from the speedo to derestrict it but all forums say don't cut it off..... someone kindly cut ours off for us and I am at a loss as to what to do there now

I have tested the ignition with a multi meter and its doing the right thing in that it connects 2 wires together on one side and 2 wires together on the other. That's why I was looking at the Magneto / Stator to see if the issue could be something there shorting.

Simon

[Nobby the Bastard]

[-]

If it's anything like my TZR250's the kill switch is actually open circuit when on "run". When you put it to "off" it closes the circuit and sends a pulse to the ECU to tell it to switch off the spark.

This could be why you get one spark. The kill switch circuit is permanently shorted out.
____________________
TZR250 2MA road, TZR250 1KT road, TZR250 2MA race, TDR250, YZF-750R Boost colours.
Jaguar S Type 3.0 V6 Sport R, VW Transporter T5 GP LWB Shuttle 140ps DSG.

[SiWard]

Hi Nobby, ignition off breaks all connections...… ignition on connects red and brown and also connects blue/yellow to blue/black.

[Nobby the Bastard]

[SiWard]

yes I have tested it, via a multi meter for continuity to all the wires, the switch is definitely working as it should. (I am 100% positive)

The spark only stops when we connect the battery up, if we disconnect the rectifier, ignition, the stator charging wires, the battery and the power valve it still sparks.

Its doing our heads in...…….

[Robby]

First off, one problem at a time. When everything is installed and connected up properly, does it work normally? Are we chasing a real problem here?

Secondly, I'd be looking for a frame earthing problem. If it behaves when the battery is connected, then something is managing to use the loom earth back to the battery. If the loom isn't connected to the battery, then it can't do that.

Frame earths are always a pain in the arse. Hidden away behind things, often where rotten wires get pulled out of crimps when you dismantle something else. The good side is that it's easy to add more. I tend to add a new earth cable from the battery negative to the frame, and also add in a new earth from the loom to frame at the headlight and tail light.

[SiWard]

Hi Robby, good advice, lets start at the beginning and work through with some method.

Current state of the bike is its stripped down, frame, engine, forks wheels and wiring loom in place missing is all the lights, speedo and rev counter, side stand switch is missing, dead switch is shorted and REED Switch is missing.

Im happy to go either way, I can put everything back on or strip more off, I left all the lights off to reduce the number of wires to trace while we tried to fix this spark issue but I can easily put all that back on if you think I should start from all built.

When I got the bike they were all on except the reed switch, side stand switch, rev counter and ignition, eBay advert said simply reconnect wires and away you go...... yeah right lol.

This said we (my son and I have had 4 of these in the past 10 years) so we know them pretty well Never seen anything like this before though.

So do I leave it with the minimum running wires or put it all together and work back?

Im in the hands of you guys......

Simon

[SiWard]

By the way I have had the loom off the bike and tested every wire and connection, end to end for continuity. then put it back on the bike with the same result as I started with, personally I don't think its a wiring problem unless it relates to the reed switch but I cant see that cutting that off would do this.

[Robby]

Its hard enough to trace a wiring diagram normally. Its even harder when bits aren't plugged in. Even worse when some bits earth direct to the frame, but the wiring diagram doesn't show it (does happen, if it earths by having the unit bolted to the frame rather than by using a wire).

So put it all together and see if it starts behaving. Something in the current setup must be providing 12v to the CDI down the blue and yellow wire.

If it was me, I would be replacing the ignition switch.

[-]

[SiWard]

Thanks for all the ideas and replies, I’m planning to do more investigation tomorrow and will update on how things go.
Simon

[SiWard]

All, Its been a good day, I have managed to fix the bike, the problem was traced to a wire in the loom that was broken but made an intermittent connection, As I said I had already removed all the wiring loom and laid it out then tested each and every wire for continuity, all checked out OK, put it back on the bike and wired everything up but still didn't work, so today I worked through it again on the bike testing each and every wire and suddenly found one that didn't have continuity it was broken where it wrapped around a bend on the frame.... very frustrating but very satisfying to hear it run.....

Thanks to everyone for their suggestions and help,

Simon