http://www.bikemotor.com/
according to their site, these will go about 25-30mph. You could use the
pictures as references for your own design.

good luck,
walt

wrote in message
oups.com...
because of the high proce of gas, would putting a motor on a bicycle be
practicle to get to work a few days a week? I live about 18 miles away
it is all highway with a wide berm for bicycles. I have a spare 5 horse
motor from an old tiller. Could I mount a bracket and put it above my
back wheel to drive the back wheel on my 10 speed mountain bike? Would
I be able to pedal it home if the engine failed? How would I rig a
clutch of some sort or would I even need it? Seems like an interesting
project.

How fast could you go with a 5 horse motor?