Stihl MS 251 WOOD BOSS Instruction Manual - Page 37

Releasing the chain brake felling cut. The chain brake will operate only if it has been properly maintained and the hand guard has not been modified in any way. Check operation of chain brake Winter Operation English Before starting work: Run engine at idle speed, engage the chain brake (push hand guard toward bar nose). Accelerate up to full throttle for no more than 3 seconds - the chain must not rotate. The hand guard must be free from dirt and move freely. Chain brake maintenance Preheating the carburetor N Remove the shroud - see "Shroud". At temperatures below +50°F (+10°C) 2310BA000 KN 143BA012 KN N Pull the hand guard back toward the front handle. NOTICE Always disengage chain brake before accelerating engine and before starting cutting work. The only exception to this rule is when you check operation of the chain brake. High revs with the chain brake engaged (chain locked) will quickly damage the powerhead and chain drive (clutch, chain brake). The chain brake is designed to be activated also by the inertia of the front hand guard if the forces are sufficiently high. The hand guard is accelerated toward the bar nose - even if your left hand is not behind the hand guard, e.g. during a The chain brake is subject to normal wear. It is necessary to have it serviced and maintained regularly by trained personnel, such as your STIHL servicing dealer, at the following intervals: Full-time usage: Part-time usage: Occasional usage: every 3 months every 6 months every 12 months N Use a screwdriver to pry the shutter out of the summer position (s). N Fit the shutter in the winter position (r) with its opening facing the chain saw - the shutter must engage audibly in position. N Install the shroud - see "Shroud". Heated air is now drawn in from around the cylinder to warm the carburetor - this helps prevent carburetor icing. 2310BA001 KN MS 251, MS 251 C 35