Understanding how to properly tension, or tighten, your McCulloch chainsaw chain is not only important for proper cutting, but essential for safety as well. A loose chain can suddenly jump the bar and cause damage to the saw or the person operating it, even with an attached chain-catcher -- a safety-device designed to do exactly what the name implies. Make checking and adjusting the tension of the chain a part of your regular maintenance routine, and keep handy the combination wrench/screwdriver designed for your saw for quick adjustments in the field.
Tightening a Chain with a Tension Screw
Turn off the McCulloch chainsaw and set it down before adjusting the chain. Disengage the chain brake, if applicable.
Loosen, but do not remove, the two bar nuts over the clutch cover to relax the chain, using your saw's combination tool. When completely loose, tighten the nuts again, using only your fingers.
Hold the saw so that the tip of the bar faces upward. Turn the chain a bit to ensure it is freely moving around the bar and to dislodge accumulated dirt or debris between bar and chain. Tighten the chain-tension screw until the chain pulls snugly against the bar. Do not overtighten the screw.
Check that the chain is tight but can still move freely, keeping the nose of the bar upward. Tighten the bar nuts completely, using your combination tool.
Test the tightness of the chain by pulling it downward from the center portion of the bar and letting it snap back. The chain should not sag under the bar. Move the chain around on the bar to ensure it moves freely and without difficulty. If the chain on your McCulloch chainsaw is too loose or too tight using this test, repeat the adjustment process.
Tightening a Chain with a Tension-Adjustment Knob
Turn off the McCulloch chainsaw and place it on a flat, level surface with the chain-adjustment knob facing you.
Loosen the chain brake by lifting and rotating the adjustment-knob handle one turn counterclockwise. This automatically tightens the chain as well.
Lift the tip of the guide bar and turn the adjustment-knob handle clockwise at the same time to lock the bar. Hand-tighten the bar. Do not use tools to tighten the bar as you may overtighten and damage it.
Follow the last two steps in the Section 1 to test and adjust the tension. Return the adjustment-knob handle to its original position. Ensure it lies flat and all the knob teeth engage properly with the notches in the chain brake.