Time to check the basics: Fire, Air, and Fuel, and it is easiest to first check "fire", so:
Remove sparkplug from dead cylinder, connect the sparkplug lead back onto it and have it rest on top of the cylinder fins. You might use a bungee or large elastic band to keep it from falling/rolling off the cylinder - you WANT the metal base of the plug to make electrical/metal contact with the cylinder fin metal as it would if it were screwed in.
Use the starter to crank the engine (you can shut the fuel off as you don't really have to start it) and watch that sparkplug to see if you see a good strong, blue-ish spark.
IF you don't, then either the plug, plug cable, or the coil is most likely bad and need to be replaced before progressing further. IF you do observe a good spark, then we can move onto the other two things.
