Is it under warranty....if so take it back and insist they fix it.....if not then I would start with the exposed switches...kill switch etc...since it is rain related. Check there are no components that get road spray....WD40 is good for expelling moisture. all you can do is spray it on the suggested places when it quits to see if it does any good....also check water isn't getting onto the coil packs...
Good luck