Well the bluish smoke tells me the lower compression cylinder is shot.. Maybe check your intake connections or you ran it low on oil.. Or to long between oil changes.. Why against the 840?? You are going to have to punch out your jugs anyway.. It will cost you more to do the standard bore than the 840
Regaurdless you will have to at the very least replace pistons,rings, and bore cylinders. I would check all intake connections including the carb boots.. You engine should have not done that unless you water logged it, or poor maintenece, or bad connections. Just saying..
Merlin Motorsports custom Teryx