Interesting little electrical problem

[Roosta]

Hey all,

First up this is my first post of this forums so please take it easy on me..

I am in Australia.. I have recently (2 months ago) purchased a 2002 GG EC250.. Bike is fantastic and rides really well but had been electrically stripped down to the basics for racing purposes by the previous owner..

Here's a few pics from when I picked it up:




I wish to re-set it up as per factory with headlights, brakes, indicators so i can road register it for bush riding purposes..

I have done lots of searching over this forum and found lots of informations, and guided by this information and my own electrical knowledge (pretty good i would say) I have managed to fully re-wire the bike as per my below diagram..



Now here is my issue.. When I measure the AC voltage coming from the generator on both the Low power (Yellow) and high power (White) to ground i get varying voltages from 10vac (cold idle) to 40vac (warm revving), but as soon as I connect either of these wires to the bike loom main power feed my voltage goes to 0vac and none of the lights or anything work but the bike runs fine..

I have fed a 12VAC power source into the system at the point marked on the wiring diagram with a Pink circled 1 and the chassis and all the lights work as they should so i am confident with my wiring..

I have measured the resistance of the lighting coil/generator and it seems to be within the spec of the service manual i have..

Basically pulling my hair out now trying to think of something that it could be but yer I am hoping someone has some ideas on what could be causing my lack of lights?

Cheers,
Nik

[wence]

I see the problem.... the yellow wire has a break in it where the Y is

Joking , Have you checked the regulator?
Cheers Mark

[bergerhag]

Ok, i have a few thoughts on this. Is the AC voltage a true AC, with voltage going thrue a positive and negative phase with chassis as 0, as in the red curve, or is it an alternating positive phase as the blue? I would think it is the blue one, since using a backfed zener diode as a regulator on the red one would short half of the phase out through the forward direction of the diode. When voltage reaching high enough the zener regulator cuts it at its preset voltage, the black line, thus creating the green curve at 12V.

If your regualtor is shot or connected in reverse, the blue curve system would all be shortened to ground through the forward direction of the diode. If you then feed it a true AC by some external system, that has its own regulator, you would see the lights go on, but only use the negative phase of the red, since the other phase is shorted.

If you have access to an oscilloscope, I'd love to see a pic of the voltage when bike is running, with a 0V reference.



And I could not find a chassis connection for your lamps in the drawing, but I assume you have them grounded.

[Roosta]

Hey guys,

Thanks for the responses.. I have not checked the reg due to not being sure how to do this.. Any hints?

I have only been checking the voltages and resistances with my dmm but i have a 20mhz oscilliscope in the shed which i can dust off n check the ac curve..

It would be so much easier if it was DC ha ha..

I actually suspect the previous owner has tried to do some electrical system power mod n killed the ac generator..

Cheers,
Nik

[Neil E.]

I agree that the voltage regulator/rectifier hookup is suspect. When I scoped my stator output (using an ancient 20Mhz CRT scope), the waveform was true AC. On the yellow wire I had 25V peak to peak and on the white wire I had 30V peak to peak at moderate RPMs. With the motor rev'd up, the amplitude increased beyond the range of the scope. I'm sure the stock reg/rect is half wave.

Being familiar with mains voltage we tend to think that half wave is not that good, but in reality that's because our frequency is fixed at 50 or 60Hz. A motor provides increasing frequency with RPM, so half wave is fine.

The problem must be in the reg/rect hookup or with your grounding. I don't see a battery in your diagram, so you might have dim lights at idle when the brake light is on. Based on your 10V and 40V numbers, the windings should be working OK.

[GMP]

On the USA spec bikes at least, its not even a half wave rectifier. Its a simple back to back zener diode "clipper" circuit, to limit the effective RMS voltage to around 12V (loaded). Some of the trials bikes, the Pampera, and the Euro spec ECs have a half wave rectifier, to run the flashers, horn, and fan.

[Roosta]

Ok so I dusted of my CRO and old age has had its way with the probe, so while I await my local electronics boffins to source me a new probe to do the testing i have opted to do some other tests..

Firstly I disconnected the Reg/Rect to see if that makes a difference.. No voltage ac or dc with the dmm..
Then i disconnected the generator power feed out and measure between both yellow and chassis and white and chassis and same as before get healthy voltage which steadily changes with rev's and temp of bike..
Then i figured i would try to just run a single indicator off the stator direct output (yel and white) and chassis (i keep the dmm wired in parallel to check voltage).. No light and no voltage ac or dc..

I have seen similar in stances like thins before where generators will be capable of showing voltage under minimal/no load and when loaded up just cant product power.. I am really starting to suspect a faulty generator..

Can anyone tell me if our lovely GasGas machines share the same generator as another model on the market? Also how do i get the thing off?

Cheers,
Nik

[Neil E.]

Originally Posted by Roosta

I have seen similar instances like this before where generators will be capable of showing voltage under minimal/no load and when loaded up just cant produce power. Also how do I get the thing off?

Good call as I've seen this too. Your DMM takes so little current to operate that it will measure it. Voltage and current usually go hand in hand, so I would still suspect the possibility of a bad connection. The stator could have a cold solder joint.

You need a flywheel puller with M27 x 1.0 Left Hand thread. Also a flywheel holder or use an impact gun (or hold the back brake on in gear).