Have more or less the same problem you had: Camino starts but goes out if you don't pull the throttle. Fixed that one "cowboy style" by fixing the throttle cable in a way so that that little lever on the carb does just not touch the idle adjustment screw. Now mine starts reliably and runs (too fast for idle without gas, but ok).
Now yours won't start. Since you say you have a good spark, petrol is flowing and the air filter looks nice it's either still dirt in the carb, or in the exhaust.
I'd suggest the following (but careful, never tried that, I'm no expert!): remove the left pedal, attach an electric drill instead, remove the air filter box, then spray some brake cleaning spray in where the air filter box was while you turn the pedal axis with the electric drill. Don't overdo it with the spray, I think you can over-rev the engine with it. This procedure worked wonders on my 4-cycle lawnmower; it would not start, and afterwards it ran much nicer than before.
If it does not start like this, remove the exhaust pipe and try again (careful, this can get really loud).
While you have the exhaust pipe off, put it into a big metal bowl or something, pour Diesel into it, light the Diesel up and see that the whole exhaust gets red hot. Don't do this indoors
Let it cool down and blow the dirt out with compressed air (also don't do this indoors, you won't believe how much dust you'll get out like this...).Good luck!
