The Stihl 021 is a gasoline-powered chainsaw with a one-cylinder engine. Featuring a case made of both injection molded plastic and cast magnesium, this one-man saw is rugged enough for a number of applications, including such demanding tasks as felling trees. Its anti-vibration handlebars make it easy and convenient for the operator.
Stihl's 021 powerhead features a one cylinder, two stroke engine. It has a displacement of 2.15 cubic inches and a bore and stroke of 1.6 and 1.1 inches, respectively. The cylinder is made of aluminum, although its bore is chrome plated.
An electronic magneto controls the saw's ignition system. It takes a single Bosch WSR6F or NSK BPMR7A spark plug with a 0.02 inch electrode gap. The air gap in its ignition coil, on the other hand, is between 0.008 and 0.016 inches.
Because the 021 has a two-cycle engine, it runs on a mixture of fuel and oil. Stihl recommends a ratio of 50 parts gasoline to one part oil, and requires two-cycle oil with a TC rating. They also recommend fuel with an octane rating of at least 89. The saw also requires that its separate chain oil container remain filled, to lubricate the cutting chain's motion. The saw has a one pint fuel tank and a 0.4 pint tank for chain oil.
Chain and Bar Options
Stihl recommends low-kickback chains and bars for the 021 chain saw. Their recommended guide bar is a Still Rollomatic bar which is available for this saw in 12, 14, 16 or 18 inch lengths. They recommend a 3/8 inch Picco chain with a six or seven tooth sprocket or a 0.325 inch Rapid-Micro chain with a seven tooth sprocket.