Check gap of plug and regap if needed Find where the wire off the spark plug housing and find where it goes. You can take a probe or wire tester and check for continuity... I use a multimeter, if the wire in the holder for the spark plug has no breaks in it... See what kind of igniter system it has.... Points, coil, whichever it might be, you can test the coil, or sand the points. Also check fuse if applicable for coil, see if it's bad. Some have a in line fuse.