I put what I believe to be a 1974 TL125 back together for a friend. Everything is working okay until I rev the motor and it blows both the head and tail light bulbs. It has two wires coming out of the magneto. From looking at old wiring diagrams on line, I found that the white with the yellow stripe is the lighting wire. Went on ebay and found a 6 volt selenium regulator/rectifier listed for a TL125 and purchased it. The problem is that the wiring loom has been butchered over the years and there is no plug for it. I can just wire it into the system but don't know which wires on the regulator to use. Anyone have any experience with this or an electrical engineering degree that can help me out? I've included a picture. Thanks.

Tricky to explain in writing. Electrics back in the 70s was a bit less refined than today particularly the electronic control of battery charging. If all the alternator power is used all the time it causes overcharging of the battery when the lights are off. To prevent this only part of the alternator is on all the time. This supplies sufficient power for keeping battery topped up, ignition and occasional use of horn or indicators. when lights are switched on the second part of the alternator is also switched on. A TL 125 does not have a battery but I guess a similar principle  applies

On the rectifier i your picture i assume the yellow red and pink wires are the inputs from the alternator and the pale green will supply the power for your ignition and lights.

Not TL specific but I had this problem on a DT175.  The regulators I have seen on dirt type bikes are actually voltage limiters.  Voltage from the alternator increases as rpms go up.  After about 15 volts, the regulator starts dumping to ground through a circuit to limit voltage.  The energy is dissipated as heat.  After market regulators were available and I think I used one by Malcolm Smith.  On the DT, I could run the lights on AC so this worked.  As I remember it was just one wire connected to the circuit and a ground.  Like this one.

 

http://www.motosport.com/product?psreferrer=https%253A%252F%252Fwww.google.com&pssource=true&segment=badger&key=Trail-Tech-AC-Voltage-Regulator&cc=us&adpos=1o1&creative=64385813905&device=c&matchtype=&network=g&gclid=CJO3tujwpsoCFcZbfgod1OEAuA

 

The rectifier converts AC to DC.  DC is needed to charge a battery so if you have a battery you will need that also.

 

 
 

What mcman56 says is correct, lights can run on ac and in this case the voltage is limited by a device that dumps excess voltage. 

 

Before anyone can offer any more specific advice you probably need to post the exact wiring diagram for your bike and maybe a photo of you stator.

You'd be better with one of these http://www.electrexworld.co.uk/acatalog/RG06.html

I fitted one on my XL, it's an AC voltage regulator which dumps the excess power as heat, no need to worry about batteries etc and no more blown bulbs.

Craig

TL 125 wiring diagram.doc

 

See above diagram.

 

If you do install a regulator make sure it can only affect the voltage to the lights. If it is connected to the ignition it will probably prevent sparking

Looks like Ebay advice may be wrong, no sign of a rectifier on wiring diagram. My TL did not have a rectifier but lights had been removed before I bought it.

Edited January 15, 201610 yr by dadof2

is it me...or did you need to leave the lights off for a trials bike...LOL