Quiet unobtrusive bike to run around town on

[cheshirecat]

Pulsejet (http://www.youtube.com/watch?v=cyuLM6Y8jNw)

Same engine as the old doodlebugs dropping their stuff during WW2 - you can buy these on Ebay

Or even one of these french engines (http://www.youtube.com/watch?v=yy4KH88tLSY&feature=related)

[bogan]

Those things are epicaly loud, my flatmate had a little one that had just enough thrust to move a small benchvice we had it held in. So bout 5 lbs, the noise however, was way louder than an escort engine with only headers on it (different flatmate). For that size engine, I'd hope he had earplug under his ear muffs!

[DEVVIL]

The BBDA of that would be 200m:gob:

[Blackshear]

French guy SERIOUSLY needs one of those drag car fragment shields, holy fuck.
Imagine those turbines exploding at 120,000rpm.