Does anyone know how the rocker oil feed pipes were originally constructed? I'm keen to use the original set as they have the flats to hold with a spanner whilst tightening the dome nut. But they need a new section of pipe popping in. I had guessed that the 3/16" pipe was soldered in as per central heating copper pipework - but my plumbers blowtorch has made zero impression on what I took to be soldered joints.
I'm sure I've repaired one of these with a blow torch. You can saw the broken pipe then drill it out then solder the new section in. 3/16 / 5mm copper bake pipe works.
You might need to use a MAPP gas torch: I suspect it may be a higher melting point solder/braze. And yes, those flats are nice to avoid distortion when tightening.
Make a template to ensure your repair will fit keeping the rocker feed unions in line. Cut off the old pipes and drill out the unions leaving 1mm shoulder to prevent the pipe going completely through. Clean and flux the new pipe, and apply just enough solder to make the joint without excess blocking the oilway.
The Green Sparkplug Company does 3/16 copper pipe, as well as many other loverly bits, maybe even the Banjo joints and Tee pieces..
https://www.gsparkplug.com/25ft-x-malleable-cupro-copper-nickel-brake-petrol-car-pipe-tube-plumbing-gas-1.html
Blocking the oilway is a real pain, I had to do mine twice, I put too much solder on the first time and the capillary took it into the pipe.
The joints were originally silver soldered, hence higher temperature needed than for soft solder.
Much higher, in fact. The usual simple plumber's gas torches wouldn't touch it when I tried, although a quick application of oxy-acetylene soon did the job.
Not everyone, me included, has access to or the skills to use oxy-acetylene much as I'd like to.
As I say, try MAPP gas - the Rothenburger torch available at places like Screwfix or Toolstation is compatible with both MAPP (yellow) and propane (blue) cylinders and I use both at home. I can do workbench hearth brazing with MAPP and its higher temperatures should handle silver solder easily for such a small job.
Besides it's much cheaper than oxy-acetylene!
PS. you can buy suitable fire bricks online too, highly recommended for MAPP, if you want to avoid a black hole in the kitchen table and resentful glares from other members of the household. Don't ask me how I know!
Yes building a little hearth really helps get the temp up. I don't like silver soldering brass or copper as the line between a nice joint and melting the job is a bit too fine for someone like me. Fine if its steel, there more margin. I drill out and soft solder but there's no getting away from the problem that the soft solder is not as strong and will break if there's load on it. I cut the pipes short (say 2-3") then us a flexible hose clipped to the frame as I find this more reliable than BSA's long copper or brass pipes.
This mini-project is progressing. I'm not keen on the idea of trying to solder it in situ, so my intention is to do it on the jig I've made - which needs further work to support the feed pipe. The picture with the assembly on the head was to check that the supply pipe bends clear the head steady etc before I solder it. I will be cutting the pipe fairly short and letting a rubber pipe do most of the work. Thanks for all the pointers - and fingers crossed!