Toom wrote on 02/27/15 at 03:21:07:It's almost like she is getting water in the fuel or something.
The backfires and poor running when wet are most likely electrical. The front tire throws a lot of water at the front of the engine, up under the fuel tank, and at the kick stand safety switch down at your foot. The electrical connectors are not sealed well, and it sounds to me like the ignition system is getting weak when wet.
As other said previously - start the bike and carefully start to get the parts wet.....try a spray bottle of water to be more precise in where the water goes. Don't just spray the whole bike all at once - start at the bottom and spray water on the kick stand safety, then work your way up the bike carefully trying to see what causes the bike to lose the ignition. Spray some water on the spark plug cap, wire, coil, etc. and get each part wet one at a time. Also try the left handlebar control where the engine stop switch is located.
I would also suggest you take the tank off, pull the electrical connectors apart and look for corrosion. Clean any off that you find, and then use a dialectric grease to seal and protect the connectors. Look at the decompression controller - the seal in the housing can go bad and let water inside.