Hello Kevin and welcome to the forums.
Could you give us a bit more info? Does the engine just die quickly or sputters slowly to a stop?
Some ideas for you.
1. The vent for the tank sometimes plugs with water in heavy rain. The vent hose runs behind the engine on the left hand side. One fix is to trim the end of the hose at a 45% angle to prevent water from getting up the hose and plugging it. A quick check to see if this happens is to open your tank fill cap which gets rid of the vacuum and see if it starts.
2. Electrical issues in the rain have been a bit of bother for some. Make sure all your electrical connections are tight and sealed with dielectric grease to prevent water from getting in. Check your kick stand switch for water contamination. The coils under the tank should be checked. The wiring under the seat and behind the fusebox are all prone. Grease up the fuse box also. This will prevent glitches from happening in the future.
