The problem with electric motors is that they make peak torque right from the word go. This means that your throttle and speed regulation is always going to have a switch like feel, even if you can use a voltage regulator to feed power in slowly.
Without gear reduction you only get out of your motor how fast she will turn which depending on rear sprocket can be 45 mph. However she'll accellerate like a bat out of hell. With proper gear reduction the bike will go as fast as you can gear it to.
There is a whole organization dedicated to drag racing electric cars and motorcycles and they are getting pretty fast times out of both.
http://www.nedra.com/
Killacycle has gone 9.45 seconds at 156 mph and 8.76 @ 145mph.
http://www.killacycle.com/
I would love to try this sport since it seems fairly emergent, but their nearest event is maryland. I do have a spare dragbike frame however and enough parts to make her a roller. now all I need is a jockey.....Hey AD!!!!!!!!!!
dig the video and how quiet the bike is.