Basically, I'm hoping for an informed discussion of questions like these with people who do more than bolt parts together, which would mean people who at least own a lathe and mill. However, as I said at the start, it doesn't seem very many people on Britbike fall into that category so this could be a very short thread.
I own a small RANDA lathe and pillar drill and various other tools so I hope that gives me enough qualification to try and answer question. I don't use these tools for precision mechanical work as they aren't up to the job, they are however OK for making spacers, drilling out holes etc.
In order to answer the questions I've broken them down individually as shown below:-
Beyond the pleasure that doing such precision mechanical work might bring, in monetary terms are you (me) wasting your (our) time?
Given the cost of farming out work to various machine shops, I would say you are not wasting your time and money especially when you consider that the work will have been done exactly to your own spec.
Are people who buy restored old British motorcycles today unlikely to put enough miles on them to reveal shortcomings in the mechanical work?
I think that would depend on how the bike is ridden and subsequently serviced. I imagine that most riders will ride less than 1000 miles annually and for most of the time the bike will be sitting in a warm garage and get an annual service. On the other hand, some riders will thrash their bikes relentlessly, pull wheelies and rev the bike past the red line and try cruising on the highway at 90mph. I guess that the former type of rider will not experience any mechanical failure for at least 15 years whilst the latter will probably blow the engine in a year or so.
The issue here is not so much the quality of the restoration but the fact that British bikes are fragile and don't respond well to mistreatment.
Would someone pay any sort of premium at all to buy a bike with documentation showing details of the mechanical work, or is chrome and powder paint all that really matters?
Yes I would pay a bit more if for example the bike has recently had new valve seats & guides inserted, aligned, diamond honed etc. by a renowned company such as the Cylinder Head Shop, and there is documentation to support this.
Does the average buyer of an old British motorcycle (as opposed to the average Youtube video maker) know enough, or care enough, about the mechanical aspects to even judge the quality of, say, someone else's work to install new guides and seats?
Some will and some won't but overall I think most will be happy enough just seeing an engine running with no apparent faults.
I have to say MM, you postings about the Ariel and other restorations have been extremely interesting and informative. I think you have raised peoples engineering knowledge and awareness considerably over the last few years, and who knows this may have helped to raise standards going forward. As Trevor said, I don't know how you find the time to do your machining, photograph each step and then post an almost daily update, I'm sure all the effort is appreciated by forum members.
I was hoping to read more about the Black Shadow restoration, but as you know, the VOC forum seems to be in turmoil as they try to migrate to another platform. Other than using this forum, I don't know if there is an interim alternative, but it seems like the restoration is stalled whilst you await clarity with the VOC.