have a look in earlier entries about my 4PT, WEAK SPARK especially.what a saga! klaus describes what and how to check things in there, including the coil. my coil tested on the limits but i replaced it anyway with a new genuine part, also HT lead, plug and cap.tighten up all your connections. if you test the resistance and its definately duff, i can send you my old one, as far as i know it could be fine.i changed a few bits at once so it may not have been the coil at all! might save you £45 mate.
until you sort the spark out, dont worry about the carb.if you have a good spark and still no starting then you know its a fuel problem.