My Stihl 028 won't start. It ran fine last month. So far, the following has been tried:

1. I've replaced the coil and plug. There is a strong spark.

2. I sprayed fuel into the carb.

3. I've pulled the kill wire.

4. I checked the flywheel key. It is fine.

5. I tried new fuel.

The saw won't even sputter. The piston is moving up and down as it should. I can't figure it out. With spark and fuel, it should do something. Any ideas?