Greg, James N. Kirby only made Lauson (later Tecumseh) engines under licence in Australia for a few years in the early 1970s. As far as I know none of the Kirby-Lausons was of more than 3 hp, and I have not heard of them being exported. Hence the engine fitted to an American ride-on mower would not be branded Kirby, but might have been Lauson or Tecumseh if it was not Briggs. (Tecumseh bought Lauson in 1956 but continued the Lauson brand for a while - I don't know how long.)
Having a reserve provision in the fuel tank sounds like a good idea in a small-tank, fast-consumption situation like that. It at least gives the operator the chance to drive the mower back to base to refuel, rather than running out and having to walk back.
I notice the Tecumseh V70 had a cast iron cylinder liner, like the Briggs Industrial/Commercial product line.
