FH - rocker box refurbishment

With the cylinder head coming on, it’s time to take a look at the rocker box. We won’t be doing too much, as a number of folk have told me how a BSA A10 rocker box fits straight on and is a much better design - but I don’t have one of those.

We’ll start by stripping out the rocker shafts and cleaning the box.

While the lathe is in action, we’ll replace the 5/16" BSW stud that wasn’t holding the cover on - the covers are held on with a special 1/4" CEI sleeve nut. What we need is a stepped stud, like the original in the inlet side but with a 5/16" BSW thread to go in the aluminium casting. Somebody has already recut the thread in the casting to suit the replacement stud.

We'll start with a bit of 5/16" mild steel round bar. Because it's 1/4" in diameter for most of its length we'll need to be careful when we turn it. What we will do is use the travelling steady on the lathe to support the slender quarter inch section as we turn it to size.

 This turns out pretty well especially when we make a finishing cut with a round nose tool. Cutting the 5/16 BSW thread, I've set the die to its largest diameter such that the thread is a little oversize.

This is where the oversized thread pays off - when it's fitted in the box the the stud fits quite tightly and hopefully won't back out.

The next step is to get the box in the cleaning tank for degreasing; we'll then examine it for damage and polish the outside.