Hello from a new member with a sparkless M18s .

[willowbedone]

A bit more info would help !! What year coil ignition or magneto

[Groily]

Continuity across open points is right on a magneto, wrong on coil ignition. I am guessing from reading between the lines that you have a Lucas N1 magneto fitted. The resistance of the low tension winding in a mag is what you will see across the points when open. Half an ohm roughly, and hard to detect compared to 0 on most meters. Closed points - ideally 0 ohms but same caveat - and if the points are mucky you'd be lucky to see much difference even with a sensitive meter.
I'd clean points to squeaky clean to get rid of any oxidisation, put he sprung opening one back in place with a 12 thou gap and try again before doing anything else (assuming it is a magneto). Also check HT lead, plug cap and plug to be sure they are continuous.