possible AC magneto problem

[jan.van.gent]

Hi everyone.
I have an issue with the electrics of my 2005 WR250F.

 

Past Sunday I went for a ride with the WR. At the end, I noticed my front-light was nog functioning anymore. However, rear light was still  ok.
I checked the bulb, which was fine.

I did the AC magneto check as described in the workshop manual (measure the resistance between the yellow wire and the ground). This was about 8 Ohm. Which seems to be to much (should be around 0.2-0.4). I ran some more tests, checked a few things,...

The battery was still charging (14.2 V when engine was running, 13.5 when engine not running)

After a while, suddenly the tail light stopped working to. The battery was also not charging anymore (13.5 V while running).

When I measured the resistance of the lightning coil, this time it was infinite.

 

Looks like I witnissed the final spasm of the lightning coil? Could this be?

 

Could this failure have anything to do with a replacement CDI I've put in last week? See: https://www.thumpertalk.com/topic/1118976-timing-map-wr250f/

The engine still runs good, on battery power. So ignition etc. still functioning properly.

Or can a CDI not cause any damage to this lightning coil?

 

100% sure it is the lighnting coil or could it be something else? 

 

Thanks for your advice!
 

[ronbuell]

regulator rectifier, #14 in the wiring diagram, pg 6-1.

Bad regulator will take out the magneto.  I've seen it before in association with shorted wire to the headlight.

[jan.van.gent]

Thanks for the suggestion. How dan i check the Regulator rectifier function without AC current...

The thing is, the battery was still charging correctly while the headlight stopped working already.

[ronbuell]

You do what's called a front to back ratio on the regulator.

 

There are diodes on the regulator that allow the AC current to flow in one direction, but not the other.  That's what creates the positive and negative voltages out of the alternator.  Otherwise, all you get is AC out of the alternator.

 

The diodes are inside the regulator, and due to their connections, they direct only + to go to RED and only - to go to BLACK.

The catch is the system is in balance when the headlight is working.  When its not, the excess voltage is put back into the regulator and it gets really hot.  Usually the heat destroys the regulator part of the circuit in the regulator, allowing the excess to go back into the AC coils and melts them.  So its a Chernobyl.... this piece fails, taking out the other.  The fix is usually you have to replace both.   

 

SO, to test, you take your multimeter and test with black lead connected to ground and red lead on meter to yellow, then to white leads.  Then you reverse the test meter leads and test again.  You should get nothing in that direction.  You have to do both sides out, negative or ground, then the RED + side.

 

Usually the failure mode is you don't get any output, but you could get flow in both directions.

You could also google rectifier test for Suzuki 750/850 or Kawasaki KZ900/1000 or Honda Goldwing 1000.

Tests are all the same.

 

As long as the headlight is working, it uses enough of the voltage to keep the system in balance.  I've been able to swap the tail light with LEDs and get more voltage to the headlight for a brighter headlight.  Has worked for years.

Edited February 26, 2015 by ronbuell

[jan.van.gent]

You do what's called a front to back ratio on the regulator.

 

There are diodes on the regulator that allow the AC current to flow in one direction, but not the other.  That's what creates the positive and negative voltages out of the alternator.  Otherwise, all you get is AC out of the alternator.

 

The diodes are inside the regulator, and due to their connections, they direct only + to go to RED and only - to go to BLACK.

The catch is the system is in balance when the headlight is working.  When its not, the excess voltage is put back into the regulator and it gets really hot.  Usually the heat destroys the regulator part of the circuit in the regulator, allowing the excess to go back into the AC coils and melts them.  So its a Chernobyl.... this piece fails, taking out the other.  The fix is usually you have to replace both.   

 

SO, to test, you take your multimeter and test with black lead connected to ground and red lead on meter to yellow, then to white leads.  Then you reverse the test meter leads and test again.  You should get nothing in that direction.  You have to do both sides out, negative or ground, then the RED + side.

 

Usually the failure mode is you don't get any output, but you could get flow in both directions.

You could also google rectifier test for Suzuki 750/850 or Kawasaki KZ900/1000 or Honda Goldwing 1000.

Tests are all the same.

 

As long as the headlight is working, it uses enough of the voltage to keep the system in balance.  I've been able to swap the tail light with LEDs and get more voltage to the headlight for a brighter headlight.  Has worked for years.

 

Hi,

 

So that makes sense! 1 week ago one of the connection of my headlight was broken. So I soldered it back and it worked again. But maybe there have been just a bit of short circuit, which might have damaged the regulator. So after a while it stopped functioning properly.

The failing regulator resulted in non functioning head light. This resulted in damaged AC magneto.

 

I performed this test: 

When I performed this test when the tail light was still working, but the head light wasn't, the resistance was about 8 Ohm (instead of a good 0.2-0.4 Ohm as it should be).

Now (tail light not working, not charging anymore) the value of the resistance is infinite.

So I suppose my stator is toasted.

 

How can I now check if the regulator is still OK? Since I suppose the test for the regulator (image below) does not apply anymore since the regulator does not get any AC anymore. And if no input, also no output, right?

[Otto1]

I have never heard of excess voltage being put back into the system??. The system will generate AC voltage to the redline with more at higher RPMs. THe Rg/ REct is there to do just that, regulate and rectify the AC current to run the bike. I run with my light off all the time with no issues. Reg/Rect are solidstate and they just fail.

 

I had the same issue. THe WR uses DC current to charge the battary and run the bike. The lights are run from the AC side of the system. Start the bike and put your meter in either the head or tail light socket and check the voltage with an 20V AC setting. while you rev it up. I can almost guarantee it will spike . When it spikes while you are riding it blows the bulbs out. If there is no voltage than you still need to replace the Reg/ rect.  and maybe the stator if it's toast. The reg/rect is a less expensive place to start.

Edited February 26, 2015 by Otto1

[ronbuell]

Ooops, I got part of it wrong.  I was thinking it was a total regulated system and lights were on 12 volt like street bikes.

After I studied the schematic, I see that Otto is correct.  The lighting is separate, runs on AC, not 12 V.

 

You still need to test for the yellow lead coming out of the mag.

The book doesn't say this, but I'd check for continuity between the yellow lead and ground.  Unplug the plug to the regulator rectifier AND all the lights.  If you get no resistance, IE continuity, then the alternator coil on the lighting side shorted out.  The coil shouldn't show any continuity to ground .... if you unplugged all the lights and regulator rectifier.

[RickyStator]

Ooops, I got part of it wrong.  I was thinking it was a total regulated system and lights were on 12 volt like street bikes.

After I studied the schematic, I see that Otto is correct.  The lighting is separate, runs on AC, not 12 V.

 

You still need to test for the yellow lead coming out of the mag.

The book doesn't say this, but I'd check for continuity between the yellow lead and ground.  Unplug the plug to the regulator rectifier AND all the lights.  If you get no resistance, IE continuity, then the alternator coil on the lighting side shorted out.  The coil shouldn't show any continuity to ground .... if you unplugged all the lights and regulator rectifier.

the lighting coil is grounded, there should be between 0-1 ohm between yellow and ground

[jan.van.gent]

So, this evening i did a lot of measurements.

 

Seems like the regulator is OK. Switched my regulator with the regulator of my dad's WR250F.
Next thing I switched is the CDI (I have aftermarket cdi), nothing changed.

Then, I checked the resistance (this time took my time to measure it decently) of the ac magneto (yellow wire) and this was between 0 and 1 so stator should be ok.
I measured the restance between yellow wires (coming from the magnto and going to the regulator), 0-1 resistance so cable should be OK.

 

I noticed, when I unplug the yellow/white cable comming from the stator, the engine stops running (dad's WR). However, mine doesn't because my aftermarket CDI is battery powered. So I could measure the AC voltage comming from stator: 5-6 V at idle, and Climbing while revving. I switched my CDI onto my dad's bike and I noticed that the lights were working (as expected) and as soon as I unplugged the yellow/white cable from stator, lights were off (as is charging). With this cdi, now i could measure the voltage comming from stator: 5-6 V while idling. So about the same so seems like my stator is still ok since performance seems the same. However, this is ofcourse when not under stress.

 

Then I took a closer look to my headlight bulb, seems like it is broken... I will replace it asap, but I suppose this cannot cause the charging system and taillight not to function? Or can it?

 

Any further ideas?

I also found this in the wireloom: (also on my dad's WR). Could'nt find it in the schematics. What is this?

[fatfastroger]

I think this is the doide(s) for the starting circuit, mine has them too.

They look exactly like mine do, even the white tape and badly wrapped black tape.

 

Why did you swap your CDi ? Was  it intermittant or dead ?

 

My bike will run for 10mins then stop - thinking I have electrical issues too  might be the ignition coil breaking down under heat

[jan.van.gent]

Turned out it was just faulty wiring and bad light bulbs... I replaced al the dodgy wiring from previous owner and now everything is excellent.

 

@fatfastroger: the CDI worked sometimes, but not always. I diagnosed this problem by switching my CDI with my fathers WR250 CDI, and it was clearly the CDI.

So i bought myself a ignitech programmable CDI (€170, about 140 dollars I guess)? Very happy with it! Bike runs great!