Points gap

Good morning all and a Happy Christmas,

Many years ago I had timing problems as one cylinder would fire at idle and the other not. She seemed to run reasonably well as the revs rose but the idle did me in. I still have the original CAV magneto with the little round ceramic (or something) ring operating the points.

I subsequently found several things which impact the smooth runnung of your ABC aside from the leaky manifolds, wobbly valves etc.

First was the little ring. Mine had 'flat' spots on it!!! This meant that at times The points didn't open or had a reduced gap meaning the timing changed. Two, the two little slopey cam things on each side of the cam ring which push the little ringy thingy were NOT the same shape and, therefore lifting the ring a little further or a little closer therefore the points gap changed. Points gap on No 1 cylinder is NOT necessesarily the same as No 2 for the correct timing. Three, the little ringy thingy has to be EXACTLY the right size!! The hole in the middle allows the points to close, just, when the cam goes past. Any more and the thing slops around and must cause excess wear. The outside diameter must be correct as well or the whole shebang is not happy.

When I realized all this, addressed the ring and made a new one from teflon to test, stoned the cams so the points opened on the ramp ewxactly at 180 deg (don't worry about the gap) and set it up she ran better than my mates new BMW.

I hope this helps someone and any further comments on where to actually FIND a new magneto ring made from the correct material, if anyone knows what it is, would be appreciated.

Regards

Guy