Stan,
I asked the same question a while back. It turns out there are several reasons the compression changeover valve was unique to the early British Listers, and didn't catch on with other manufacturers after the patents expired. They are the same reasons you don't see the changeover compression valves on most Indian 'roids. The cooler valves tend to accumulate carbon and eventually the abrasive carbon eats the packing around the changeover valve shaft and the valve leaks compression at the time you need it most. That was a problem even with the British engines. Injector and pump production techniques and materials also improved over the years. Newer injection pumps and injectors produce finer and more consistent spray patterns than did earlier (pre-WWII) models, so the troublesome changeover valve was discontinued and not missed.
Another thing to consider is that these engines are assembled from parts that are purchased from many manufacturers, much like PCs are today. The piston pin location and rod length or the head clearance must be modified in a changeover valve engine. Unless the manufacturer makes these uncommon parts for that application, AND the assembler picks the right parts specifically intended for this configuration, what you may find is that the engine runs fine in the high compression "start" mode, but smokes badly and doesn't want to start in the lower-compression "run" mode.
As Willem just pointed out, his engines have the changeover valves. Most don't think the bother is worthwhile.
Quinn
