When you say it won't start, I assume you mean it will turn over smartly, but not fire. I've never had trouble starting my cub in cold weather. With a good battery, good fuel and a clean air filter, there isn't much else needed. Of course, your timing, coil, points and condenser all need to be in decent shape. It's not like it's a diesel. I'd suspect things like water in the fuel line (as you've speculated), weak battery (or poor connections to it), bad coil/condenser, marginal gap on the points. First and foremost, make sure the battery is fully charged. If it's turning over quickly, then fuel is the next place to look.
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