Here is another 2WD bike called the 2x2x2 built by a very clever Australian, Ian Drysdale, who is also responsible for the Drysdale V-8 bike based on two FZR400 top ends. It was built over 20 years ago before the Ohlins or the Christini. It uses 2 wheel steering and similar hydraulic drive to the Ohlins bike.
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Here is another 2WD based on a CR500 built by a friend of Ian's.