recently brought sthil ms180... basic model without primmer bulb or "easy start". Hard to start on first two uses... both for small jobs. Now can't get to start at all. Have removed and dried spark plug. followed starting procedure countless times but won't even start to "fire". have used sthil strimmers, blowers and hedge cutters for years with very few problems but this is really ticking me off. Has correct mix of 2 stroke in tank and plenty of it. anything else i can try to aid starting and get it going?