Welcome to Myrons Wiring Diagrams. Mopeds have strange electrical wiring. Many have “secret” wires that must be grounded to run. Many have switches that normally would turn off something, but instead they turn on something (brake light or horn). Most of the wiring diagrams explain this, when it applies.
This “secret wire that must be grounded to run” system is only on most 1970’s and 1980’s US models. The reason for this craziness is that European mopeds do not need brake lights, but US ones do. So many kinds power the brake light from the back side of the ignition source coil.
One kind, Puch 77-later, 6-wire, powers the horn from the back side of the ignition source coil. So on a 77-on Puch, if you unplug the horn and push the horn button, the engine dies.
Besides loosing spark, older mopeds also often burn out light bulbs. That is because a magneto generator alone, without a battery or regulator, ranges from dim lights at idle, to bright at full speed. So your bulbs are either too dim, or else they burn out a lot.
Modern (1990-later) mopeds don’t have the old moped wiring problems. They run a more powerful magneto, 70-80 watts instead of 30-40. All the lights run off one wire, with a 12VAC voltage regulator. To keep the voltage below about 13V, the regulator passes any excess current into the frame where it’s mounted. So when most of the lights are off, the frame is being warmed a lttle. This “regulation by wasting” system is common on motorcycles but not automobiles.
Also nothing that the lights do ever matters to the ignition. Magneto ignitions after about 1993 are CDI (Capacitor Discharge Ignition) instead of points. They’re also maintainence free and have easier starting.