I soon found out that GS150s were not known for their electrical systems. The bike will not start if it does not have a charged battery and it has a habit of flattening the battery when left alone. I think this is because when the engine just happens to stop with the points connected there is a slight drain on the battery regardless of the ignition switch position. The rectifier was badly damaged and after a bit of help from the International Scooterist BBS I decided to make one from scratch with more up to date parts. I also included a battery disconnect switch to keep the battery fresh when it put in the garage for the night.
I didn't have any electrical literature for this bike so we had to solve the electrical problems working backwards from the engine. I found a beautiful NOS switch from First Kick Scooters and set myself up with a multi-meter and my brother's help to figure out the ignition key settings. Below are the ignition switch locations that we worked out:
The direct lights on this bike are a bit of a joke and I found myself always using the lights directly off the battery when driving at night. The GS150 uses a 6 volt system and can only really provide enough juice directly off the stator when running at high revs. When you are at a stoplight the direct lights are almost nonexistent.
We built a new rectifier from scratch and I will post a how to page in the near future. If you want to convert the bike to using no battery at all click to link to a how to article on the Piston Ported Vespa page or here is a link to someone who made a 12V conversion.