Testing for spark is pretty easy. First, you can just shoot some starting fluid in the air intake. About 2-3 seconds should be plenty. If the bike starts up, even for a second, your spark is probably good. If you don't have any starting fluid or don't want to do that, pull a spark plug wire and jam a screwdriver up the spark plug boot. The spark plug boot is the rubber part of your spark plug wire, that fits over your spark plug. Turn your bike on and hold the base of the screwdriver shaft close to the head of the engine, or a part of the frame. Hit the starter button. You should see a nice fat blue spark leap from the screwdriver to the frame (About 1/8 inch or 3mm). Test all the spark plug wires. What do you see?