Temp. in the 40's is not really "cold"...

Make sure your glow plug battery is fully charged so that the plug (O.S. type F) glows bright yellow-orange, then crank the snot out of it with an electric starter with the throttle set at about 1/4 and if the carb is not badly mis-adjusted it should start.

If that don't do it, check the valve timing...that's about the only other thing I can think of right off hand.