Have you took the spark plug out of the head, attached the wire, laid the plug on the head and seen spark? The spark needs to be between the 2 electrodes. By holding plug/wire about a 1/2 from the engine is should throw a nice blue spark that far. Any doubt, stick another plug in it. 2 strokes are snivelly as hell about plugs. How old is the gas? Over 6 weeks and it can begin to degrade. did you replace crank seals? an air leak around the crank will cause grief too. Could it be flooded? Is the plug wet? If not, drop about a teaspoon of fuel down the plug hole, install plug and see if it fires. While plug is out, stick finger over the hole and crank engine, it should blow your finger off. Make sure the plug wire is not near finger when doing this, as neighbor kids may learn new words. Hold your hand over the back of carb while cranking, is it sucking or blowing? If not sucking it could be reed valves. Could you have installed piston backwards? It's been done before. On some reed valves if not sealing, you can turn them over and they may work. Is the gasket on the correct side of the reeds?
