Check your spark plugs/leads for water ingress, did you air up the parts, did you use compressed air to blow off excess water from electrical components?
What do you mean by "it won't start after 4 to 5kms" what are you trying to tell here
1) It cranks, but doesn't fire up or
2) It's completely dead?
Either way you're creamed, check for loose spark plugs/leads, water ingress and use compressed air next time you wash your bike. The bike has many exposed parts, you never know when it might short or go kaput.