MOPED ARMY

Are you using 6 volt bulbs on your motobecane after January 1st 1978 the lighting became 12volt. Are you sure that you are using 12volt bulbs otherwise you will keep blowing out bulbs.

Do you have a link to any info on that part? You say it is both a rectifier and a regulator; but it looks to me like it's just a regulator.

Most regulators only have two terminals - power and return ("ground", usually the frame on a moped). They work by shunting extra power back to the return, typically with a reverse biased zener diode (or a stack of zeners, possibly with a forward biased signal diode or two to fine tune the regulator voltage).

I can go into more electrical theory here if you like, but the bottom line is that they are indeed intended to be inserted into the circuit with just those two terminals, power and return.

If you are blowing 12V bulbs on a 12V system with a 12V regulator, then your regulator either isn't working or isn't installed correctly. Make sure the frame connection is on clean bare metal.

What I do is apply a higher voltage than the regulation voltage with a resistor in series to limit the current, then check the regulator voltage with a DMM to make sure it's in spec. Two 9V batteries in series (~18V) is great for a 12V regulator; throw in a 1kΩ resistor in series between the battery and the positive terminal on the regulator and you should be in business. You won't want to use any random resistor here, too small and it will burn up, too large and you won't have enough current to turn on the regulator. A 1kΩ is a good balance for most diode based regulators (36mA in this case).

In theory a 6V bulb would work in place of that resistor, but I haven't tried it. It should light up with a good regulator. I'd use a low wattage one, like a little 1W speedo light or something. 9V batteries are pretty wimpy.

If the regulator is bad, or if you aren't giving it enough current to turn on, the voltage across it will read the full 18V. If it works and the test setup is correct, it should read about 12V. Many "12V" regulators are really designed for charging 12V batteries, and can regulate at voltages up to about 14.5V.

As you know, moped magnetos don't produce true AC power, so DMM voltage readings on a running bike aren't very useful. The scaling factor between what the DMM says and the peak voltage varies by configuration; how many coils, how physically large those coils are, how many magnets, on the flywheel, how large the magnets are, etc.

This is also complicated by the fact that there are many ways to build a regulator. A simple zener diode regulator can be checked with a DMM in diode mode, but who knows if that's what's going on inside these mysterious lumps of epoxy.

The water analogy might work better here. Imagine a big pipe filled with water, and your bulb is an open faucet. A regulator is like a piece of pipe ahead of the faucet that diverts some of the water away, reducing the flow that comes out of the faucet.

I don't know if you got it sorted. I am an electrician of 25 years, just a few quick thoughts. If you have not installed the regulator use it, bulb life depends on it. As already mentioned try mounting the regulator, notice how the ground tail and device have the same size hole? Mount the regulator and install the ground tail over it. If the stator has a ground wire to the frame try using that point to install if it fits. The regulator may need to grounded at the sheet metal part and the tail to work. This may also help pull heat out of it as well. A good spot with some air over and little splashing would be ideal. The other thing to check is the grounds, when you hit the kill switch all that CDI voltage needs to go somewhere. If the frame ground is intermittent or weak you may be dumping it through the bulb, the power wants to go somewhere to ground. The truth about regular bulbs these days is that they are just junk. You may just need to run a 35 watt bulb with that kit, the light may be dim at idle and low RPM but may bring things into balance and take some load off of the regulator.