Fixing busted head fins

I got a couple heads from a 1989 R100GS for the salt racer. These are the ones to have since they have the so-called ‘D ports’ and have larger intake spigots since they take 40mm Bings. Got them cheap because one of them was busted up: 4 broken fins, a cracked 6mm hole that takes the rocker cover stud and a stripped spark plug thread. Other then that, they were  OK!

Aside from the broken fins, you can see where I welded up the rocker cover hole ready to face and re-drill:


The process involves TIG welding a bead on top of  the broken fin edge, then another bead on top, then another, then another….until a thin wall is built. Then into the mill to have the sides shaved to the correct thickness then another couple beads and repeat.



And after quite a few hours of welding, milling and filing:





4 replies
  1. Dewey Vicknair
    Dewey Vicknair says:

    Excellent work, those fins look original. 4043 is what I used on my project. I have a question about the salt bike.
    What is the volume of your custom airbox?

    • adrian
      adrian says:

      Thanks Dewey,
      I got a figure of 5L from from a guy here in Aussieland that has raced an airhead on the salt. So I’m using that as a starting point. I’m also hoping for some ram effect but don’t have high expectations since, as you probably well know, these things are notoriously hard to get working and require lots of experimentation. At least I might get marginally cooler air with those scoops away from the engine.

      BTW: been enthralled with your combustion chamber work. And note that you plan to use an electric pump to suck some vacuum into the case. Udo Gietle used an interesting system with a tube protruding into the primary pipe exhaust flow letting Mr Bernoullis suck a vacuum into the tube…


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