get a mighty vac at your major part store. pull the carbs off and put a small vacuum hose through the piston into the crank and pump the oil out. If you burn it out you load your silencer packing full of oil and after a while under heat could become flammable.
Or you could pull the top end back off and stick rags in there to soak the oil up.
When I did mine I dumped some Klotz in there. than soaked it up before install.