The carb is held in by a pinch screw that will on occasion shake itself loose causing the carb to become loose. You will pull to much air into the engine.

Hold your finger over the exhaust and pull a few times or pull the fuel tube off the exhaust and blow into it to get fuel to run to the carb. Once it hits the carb blow just a little bit more to make sure the fuel is getting all the way in. You may flood the engine doing this but thats an easy enough fix.

You can also try taking the glow plug out and dropping a few drops of fuel into the cylinder.

If you do all this stuff with the engine needles set at factory settings you should get it to start. Does the engine fire at all right now?