The 025 model is a chain saw that was produced by Stihl beginning in 1991. It has been discontinued, but it's a saw that can still be found for sale on the secondary market.
The 025 is equipped with a single-cylinder, two-stroke engine with a displacement of 2.77 cubic inches, a bore of 1.7 inches and a stroke of 1.26 inches. This engine is bigger than those of the related 021 model, which has a displacement of 2.15 cubic inches, and the 023, which has a displacement of 2.45 cubic inches.
The 025 is equipped with electronic magneto ignition, all-position diaphragm carburetor and integrated fuel pump.
The saw's powerhead, without a bar or chain attached, weighs 10.1 pounds.
Bar and Chain
The 025 can accommodate 12-, 14-, 16- or 18-inch bars, and it came equipped with a Stihl reduced-kickback bar with a Rollomatic sprocket nose that was compatible with 3/8-inch Picco or 0.325-inch chain pitches. The saw is also equipped with a fully automatic, speed-controlled chain oiler.
Safety and Convenience Features
The 025 is equipped with a chain brake that can be operated manually by the user, and it is also activated automatically by inertia when the hand guard in front of the handle moves suddenly toward the nose of the bar, as may happen when the saw kicks back.
The saw is equipped with vibration-damping motor mounts that reduce the amount of vibration transmitted from the running motor to the saw's handles.
Stihl specifies that the 025 be fueled only with unleaded gasoline and a high-quality oil intended for use in two-stroke engines at a ratio of 50 parts gasoline to 1 part oil. To achieve this ratio, combine 2.6 fluid ounces of oil with each gallon of gasoline, adding the oil to an appropriate mixing container first, followed by the gasoline.
Two-cycle engine oils are designed for high-performance engines such as those in chain saws, and they will help prevent problems such as pre-ignition and ring sticking.
Stihl also recommends the use of gasoline with a minimum octane rating of 89 in the 025. Use of gasoline with a lower octane rating, the manufacturer claims, increases the chance of pre-ignition, high engine operating temperatures and piston seizure.