Check your glow plug. Remove it and plug in into your ignitor, carefull...don't burn your fingers. Hold it with a pair of needle nose pliers on the side and plug it in. You should see it glow bright red.
If the plug is good make sure you are primed, if there's no fuel in the engine it's never going to start. If there is no fuel, check your fuel line. Remove it and blow thru it to make sure.
Make sure your carb gap is cracked open just about 1mm. Remove the airfilter and look in the barrel. You should see just a tiny opening.
Also make sure the problem is not that your flooded. If your having to pull very hard and hold the car down when pulling then the engine is flooded. Remove the glow plug and fuel line and keep pulling until all the fuel sprays out of the head,
If all of these things are good it may come down to your high speed needle being just a bit too rich. Turn it clockwise about 1/8 of a turn and try starting it.