Troubleshooting Spark on Virago 250

Hey guys I was wondering if anyone could offer a little help on this. I have a 2001 Virago 250, and it only has spark intermittently. When it starts, it starts right up no problem and runs great. When it doesn't, it doesn't get spark and will turn over without a fire until the battery dies. It doesn't seem to change due to moisture or temperature either. I live right by the beach, and it does corrode do to the salty air, so I was wondering what would be the first thing you would check? I'm unfamiliar with the ignition system on this bike, and my online manual was on a different computer that crashed. I have already repaired the starter switch and foot brake light switch due to moisture and corrosion. Any help on the matter would be helpful. It seems to start and run fine when I'm prepared to work on it, and won't start why I'm trying to go to work. Thanks!

Tim