I was thinking of this ,too bad you don't know if this going to be a
trike or a 2 wheeled motorcycle ,or if he is going to be running a
motorcycle transmission or not ,if he built a trike then he can easily
get a generator head from harbour freight for like a couple hundred
bucks and you can buy small engines of different sizes all over the
place to power it for little bit of money and put it in a small trailer
with a small battery bank in it you could actually have almost limitless
range with it (when the power gets down just hit a switch to start the
generator run off it while the residual power is recharging the
batteries then when charged up switch off the generator and run off
batteries) if i remember right the new electric conversion kits run a 3
phase motor hooked to the stock transmission ,because they go better in
traffic
and since they do have an electric motor you can't stall it and it don't
really have a torque range so you get plenty of power to the wheels i
wont be surprised if he is building a trike like that ,but if it is a 2
wheeled bike you can still hook it up to the tranny using a 3" belt to
the tranny and adjust the sprockets for best speed
and would be a great little runabout for the local area he wouldn't have
to use gas for little runs
which could save him hundreds of dollars in gas (this would be my second
guess ) since a car uses more gas on short runs
just my 2 cents