motorbike cdi designs for 1960 english

[Stuart Williams]

Hello, I'm new here and am modifying an ariel arrow engine, one of the worst points of these engines was there unreliable point ignition system, I'm looking to build a cdi the will work of 6volts dc possibly using the original contact breakers. Many years ago I built and used on several cars the Practical electronics system that used the points and they had a capacitor in circuit to over come points bounce.
Regards Stuart

 

[Bluejets]

Just wondering what was the unreliable part of the points.
Oil contamination used to be a problem with an old Norton Commando so maybe the same here.

Cdi's tend to be a bit touchy when it comes to home built. Getting a high enough voltage in the right time for the main capacitor can be difficult.

Many of us have built successful Cdi units for model engines but whether or not these would suffice would be questionable.
Reason being the higher compression not the spark rate.
Then again. get too high a voltage in the above and you end up with a light show and sparks everywhere except where you want it.

The units I build for my own use are of 2 versions.
Firstly a simple Cdi power unit operated directly from a hall effect switch which, with a small mod can be used with points also.
Then there is the micro controlled version others have designed for programmable advance which basically tags onto the front end of the above.

One can also go the route of a simple transistor assist ignition which retains all the mechanics of your present system including any vacuum or mechanical advance.( I'd tend to go this route)
In this, any oil or similar contaminants are disregarded as the points now carry very little current.

Can you provide a link to the Practical Electronics article or have any more detail on that system?

Edit:- Further searching found a detailed transistor assist construction project pdf on a Velleman kit.
Do a search for Velleman K2543.pdf