Make sure the harness is not damaged.
Make sure the throttle trigger lock and the throttle function correctly from a safety point of view.
Check that the stop switch functions.
Check that the cutting head does not rotate while idling.
Check that the guard is undamaged and not cracked. Replace the guard if it has been exposed to impact or is cracked.
Check that the blade is well centered, sharp and not cracked. An un-centered blade causes vibrations that can result in damage to the machine.
Check that the trimmer head is undamaged and not cracked.
Check that the locking nut is tight.
Check that the blade’s transport guard is intact and that it can be secured correctly.
Using an allen key and check that all the bolts holding the various components together are tight – some will inevitably have worked loose, especially after prolonged sessions thrashing around in head-high brambles.