Electronic Ignition for R90S ?

Why Electronic Ignition

The points cam was corroded badly. I could not find a used part and a new, replacement part is too expensive. The plan is to repair the cam with an epoxy product. It would be a temporary measure to get the engine running. I will then introduce an electronic solution in stages:

• Introduce a CDI driven by the existing points system and get that working
• Replace the points system with a Hall or Infrared sensor plus suitable circuit to drive the CDI

This is the advance-retard mechanism before. Most of the cam surface has rusted away, but fortunately there is enough left to be able to reconstruct the original profile












 

I used an 8.5mm drill bit as an axle. A small file, water paper and a dial gauge and patience did the rest. It is accurate to within 5/100 mm. I'm hoping this is good enough for what I want to do. 

 This is the completed temporary cam. I did the filing by taking the dial gauge reading from a "good" original surface area and then working on the corresponding epoxied area (180 degrees from the good surface) and reducing it till I had the same reading. I could then file the rest of that section along the axis of the cam to the correct measurement. And so on till the whole profile of the cam was restored, "transferring" from "good" sections to where the corroded sections were.

  

 This is the CDI circuit diagram. Most of the components are readily available from any electronics shop. I found the circuit in "The 555 Timer Applications Sourcebook" by Howard Berlin. The book is available from Amazon.