Hi Musky, Here's a piccy so you can compare
Four remaining VW rods at the top - as you can see these have plenty of material in them to allow cutting to length, I figured they must be up to the job they were free, and I'm making them shorter so all good!
I picked my better (less bent) original rod cut it in half, tapped the cut ends 1/4 BSF, thread was a bit marginal but good enough for the job, I already had an idea what length I needed so I set it to this plus an extra 0.2mm for luck. I was a bit worried the nuts might foul the Cyl Hd gasket or the adjacent inlet rod but in fact it was fine. Built it all up dry and the job looked a goodun so happy my size guesstimate was pretty close to perfect. I only needed the one adjustable rod as I was happy 9-17/32" was ideal for the other exhaust one.
The other set was a standard set I got from Mike in Queensland, they are 8-1/2 and 9-1/2" so you can see the difference to what I needed, the photo lies but I can assure you the LH end of all the rods were in line!
I cut the VW rods at 20mm in from each end. Put each short cut end in the lathe and faced it back until I could see the end of the steel insert. Held the steel ball end in the 3 jaw and put a small live centre in the exposed end of the insert. Went in with a sharp grooving tool and progressively turned the aluminium off the insert until it let go. Faced each end of the remaining section of aluminium tube to length
less the allowance for each insert ball end 7mm x 2 from memory. The interference is pretty extreme at 0.3mm so it needed a nice 20 deg x1 lead in each end. Warmed the tube end up with a propane torch and gripping the ball end with a pair of point nose pliers I gently tapped it in to just get it started straight, then used my hydraulic press to squeeze the inserts home, one end at a time.
When I measured the finished length of the new rods they came out within 0.1 of my target sizes so pretty happy with them.
The VW rods are hollow and the inserts are drilled for pressure fed oil to run through the rod. BSA never bothered with this being happy for oil to splash around and run down the outsides. Either way I don't think the tiny 1mm centre drilling each end will have any adverse effects. I did clean the insides out before reassembly but there was very little muck in there.
As Klaus says the finished weight of these is less than half the original's so a good improvement for a race bike. All I want is an engine that keeps running!
