How do I check for engine spark?

Holding the sparkplug wire next to the engine block is one way to test the spark. Harbor freight has spark testers for a couple of bucks that work better. Another way is to remove the sparkplug, put a teaspoon of gas in the hole and replace the plug. Now try to start it. If it tries to start and or runs for a few seconds you know that you have spark. The number one cause of not starting or poor running is fuel. A dirty carburetor is at the top of that category.