2 stroke engines need three things to start & run - fuel, spark, and compression (priimary AND secondary).
If you have fuel and sparks, but no start, then the most likely cause is lack of primary (crankcase) compression, due to worn crankshaft oil seals. Only answer for this is a complete engine stripdown, in most cases. Sometimes, the seals can be replaced from outside - not sure about this particular model.
L & H screws should be set 1 1/2 turns out from fully closed, as a starting point. This should allow you to start it.
Phil Saunders, May 2012