All of my other bikes have been recommissioned. Now to some, recommissioning means an oil change and a wipe over with WD40. For me, the object of the exercise is to end up with a bike which looks old but cared for. A bike which starts, stops and rides exactly like it should.
This only works if you choose the right bike in the first place, namely one that is reasonably tidy and complete. Paintwork has to be sound as any repainting spoils the overall patina of the finished bike. As soon as you paint a tank, the original seat cover looks tatty and as soon as you re-cover the seat, the chrome starts to look bad. Before you know it, you're on the road to restoration.
Mechanical issues are not too much of a problem as you can blend the repairs in to the overall look of the bike.
I've been working on a low mileage BSA B50ss which luckily, had no major problems, but still required lots of deep cleaning and a fair bit of money throwing at it. A tin of 20/50 and an oily rag may be cheap, but properly recommissioning a bike is not. Here's a list of the main bits I had to replace in order to get the old girl sorted:
New Amal carb - £130
New oil lines - £20
New Motobatt battery - £70
New kickstart quadrant - £80
NOS chaincase - £150
New chain - £30
All new cables - £90
New petrol taps - £25
Pipe & in-line filters - £12
New handlebars - £35
New grips - £12
NOS air filter £40 (!)
Airbox - £30
Carb to airbox rubber - £12
New tyres - £120 (not fitted yet)
Allen screw set - £20
Gaskets - £15
New oil strainer - £20
Oil - £20
So that's a whopping £931 plus about 40 hours of cleaning, servicing and fettling. Was it worth it? Absolutely. The end result is a cracker of a bike which looks really nice and still retains most of its original finish. It rides like you'd expect with such low mileage and the great thing is, there'll be no problems taking out in the wet or even getting a bit of mud on the tyres.
If you're into BSA unit singles, there's a really good forum at:
www.b50.org