my 09 800 ran fine washed it drove into shop next day it fired up idled fine gave it gas it backfired white smoke rolled out from under gastank and now it wont run changed coil and plugs nothing changed ecu nothing checked spark seems to come and go checked fuel plugs where wet then cranked motor over checked again they were dry fuel seems to come and go like the spark all connections look good and dry

 

I'd pull the plug caps and clean and use a good electrical grease on them and pull all electrical connections and blow out and use the grease on them also as a start and see if it helps. Others that have had the same problem can probably add more on what to do! OPT