Make sure you can see fuel in the delivery line to your carby. You can have the best glow plug in the world and set your mixture screws till the cows come home but it aint going to do you any good if there is no fuel getting to the engine.
Put your thumb over the exhaust outlet and turn the engine over a good few times this builds a bit of pressure in the tank and fuel goes up to the carby. Yopu should be able to see it work it's way up.

If this still does not work then take out your glow plug and put a few drops of fuel straight into the cylinder, turn the engine over a couple of times, put the plug back in and try to start. If it fires, and it should, but then stops then you have a fuel delivery problem. Then open needle valve a 1/2 turn and try again.
Other things to look for.
Crap/build up in the needle seat (where fuel line attaches to carby)
Blocked fuel filter
Crap fuel.

Hope this helps Good luck

Brad