See this Yamaha patent: http://www.google.com/patents/US5806473
They had a sports roadbike 2T with 'clean-green' DFI-tech ready to go - check 'Fig 26/27.'
Their patent includes a 4T triple, which they have marketed, & ironically as a 'tribute'
style-wise to their iconic RD/RZ/TZR machines..
Kudos to Yamaha for still selling YZ 2Ts, but a road legal DFI YZ250X ( or YZ360X eh? ) oughta be a goer..