An air-cooled engine for a working machine, comprising: a crankshaft having a first end adapted to be connected to the working machine, and a second end opposite to the first end; a cylinder barrel having a first side surface that faces in a direction perpendicular to an axis of the crankshaft, and a second side surface opposite to the first side surface; an exhaust muffler provided on the first side surface of the cylinder barrel; a carburetor provided on the second side surface of the cylinder barrel; a cooling fan connected to the second end of the crankshaft for rotation therewith; a fan cover that covers the cooling fan in such a manner as to guide a cooling air fed from the cooling fan toward the exhaust muffler and the carburetor in a bifurcated manner, the fan cover having a guide opening for allowing the passage therethrough of a part of the cooling air guided toward the exhaust muffler; and an insulator separating the carburetor from the second side surface of the cylinder barrel, the insulator including a cover section that covers an open end edge of the fan cover so as to guide the cooling air toward the second side surface of the cylinder barrel, and a deflector section bent toward the carburetor for guiding the cooling air, which has been guided along the second side surface of the cylinder barrel, in a second direction away from the working machine, characterised in that it further comprises a muffler protector that covers the guide opening of the fan cover and the exhaust muffler such that a guide passage communicated with the guide opening is defined between the exhaust muffler and the muffler protector, the muffler protector having a plurality of air discharge holes (85, 86) communicated with the guide passage and arranged to discharge the cooling air from the guide passage in a first direction away from the working machine a crankshaft having a first end adapted to be connected to the working machine, and a second end opposite to the first end; a cylinder barrel having a first side surface that faces in a direction perpendicular to an axis of the crankshaft, and a second side surface opposite to the first side surface; an exhaust muffler provided on the first side surface of the cylinder barrel; a carburetor provided on the second side surface of the cylinder barrel; a cooling fan connected to the second end of the crankshaft for rotation therewith; a fan cover that covers the cooling fan in such a manner as to guide a cooling air fed from the cooling fan toward the exhaust muffler and the carburetor in a bifurcated manner, the fan cover having a guide opening for allowing the passage therethrough of a part of the cooling air guided toward the exhaust muffler; and an insulator separating the carburetor from the second side surface of the cylinder barrel, the insulator including a cover section that covers an open end edge of the fan cover so as to guide the cooling air toward the second side surface of the cylinder barrel, and a deflector section bent toward the carburetor for guiding the cooling air, which has been guided along the second side surface of the cylinder barrel, in a second direction away from the working machine, characterised in that it further comprises a muffler protector that covers the guide opening of the fan cover and the exhaust muffler such that a guide passage communicated with the guide opening is defined between the exhaust muffler and the muffler protector, the muffler protector having a plurality of air discharge holes (85, 86) communicated with the guide passage and arranged to discharge the cooling air from the guide passage in a first direction away from the working machine a muffler protector that covers the guide opening of the fan cover and the exhaust muffler such that a guide passage communicated with the guide opening is defined between the exhaust muffler and the muffler protector, the muffler protector having a plurality of air discharge holes (85, 86) communicated with the guide passage and arranged to discharge the cooling air from the guide passage in a first direction away from the working machine