Don't think it is serious, seen to many of these this year. What probably happened is that the float needle did not seat properly allowing the fuel to fill the carb and then run through the air horn into the cylinder and crankcase. What's the fix? Replace the needle and seat in the carb. Change the oil. Remove the spark plug and pull the engine over a couple of times to remove gas from the cylinder. Reassemble everything and start outside, it may smoke for awhile if there is fuel and oil in the muffler. I feel that the cause is ethanol in today's fuel which causes the seat to expand and not seal. For the last two years we have been recommending that our customers use none ethanol fuel when ever possible. Hpoe this helps.
