Maintenance make errors, just like pilots, after all we're all human. Our operation had an aircraft assigned as the night standby every night for response to any emergency off shore. The aircraft was prepped so all a call out crew had to do was pull the bungs and go. Called out early one morning for a medevac off shore, fired up the night standby and got airborne. Bit of a vertical but completed the 45 minute flight and told maintenance it could do with some tracking upon return. A look found powder coating all four elastomerics at the blade grips. Had had a head build up installed minus all four spindle bearings. Surely the vertical would have been evident during the post install track, or was a track not done, or a test flight?