What is a typical “refresh” on a bike, that I perform? First, I start taking the bike apart, “stripping” it, always with an eye on what’s missing, what’s broken and needs replacing, versus broken and needs fixing, and of course what is just fine the way it is. “If it ain’t broke…” Specific problem areas include: the headset and bottom bracket, do I need to replace them, rebuild & regrease them, or are they fine the way they are; the wheels and tyres, are they true (i.e., not bent), and do they hold air; is the frame cracked, constantly checking lugs and seat and chain stays and the head tube and dropouts; is the paint in need of touch-up, or is the patina nice enough to keep; what chrome bits need polishing, and what steel bits need brushing/abrading, to remove any rust.
This is an assessment and evaluation of the bike, tearing it apart and processing it into a box. Rarely do I ever find that a bike is beyond repair, but it has happened once – a cracked head tube, which was very disappointing. It could also be the case something is so expensive to replace that it makes the whole project not financially viable, at which point you must decide if you’re losing money, where it becomes a “labor of love”, or if you’ll just break even.
Almost always the bike simply needs to be thoroughly cleaned, bearings repacked with grease, and some consumables replaced, like brake pads, and brake and shifter cables and housing. On occasion, a rear derailleur hanger needs straightened, wheels need to be trued (“unbent”, from hitting a pothole or curb), or something is stuck (a seatpost or stem) that needs extra attention to fix.
Putting a good bike back on the road is always worth the effort. It’s finding a “good bike” that can be the hardest part.
Without making it sound easy… there’s not a lot that goes wrong with a bicycle. After all, they’ve been more-or-less perfected by the 1970s – on the whole, the formula hasn’t changed: keep it clean, keep it greased, and you’ll be flying. The humble bicycle should be considered as one of the greatest inventions of mankind.
I will say it takes an experienced eyeball to know where to look and what to look for, to ensure everything goes together correctly.