I think I read that those turbine bikes use APO turbine engines outta old military helos- too much time on the motors for flight use, but more than perfectly fine for a motorcycle project.. I think I also read that the sound these things make is freakin awesome, but that they are entirely too fast to comfortably ride- like you have to spool the motor way up to take off, and then it will go like 180 with less than 1/3 throttle or something crazy like that. Very neato though.
Also, the Jesse James bike looks like it would scrape the rocker covers on the bottom cylinders.. Man that thing is a work of art though- I wonder if that's an actual rotary motor, or a custom assembly of cylinders.
Jason