I have a Ryobi Petrol chainsaw that runs great until I fill up the Bar oil tank and then it burns oil (Bar Oil) I haven't taken it apart yet but it as it is not lubricating the chain, I'd say that the bar oil is being sucked into the crankcase.
I have never seen a Ryobi chain saw but if it has an oiler system that uses crankcase pulses to pressurize the oil tank there will be a check valve to allow the pressure into the oil tank and keep it there. If this valve has become stuck and remains open then your bar oil will be sucked into the crankcase and the saw will smoke etc. Mike
