"The 550 is a car unit."
THE GARMIN ZUMO 550 is primarliy a motorcycle unit supplied with a car mount.
There are many different devices for attachment to your motorcycle on the market. Search on ZUMO in this forum or have a look at:
http://www.zumoforums.com/index.php.
I used the simple Telferizer mount which is a bolt and RAM ball which replaces one of two bolts holding on the left hand handlebar.