The American Motorcyclist Association has put a 50+ year archive of its official publication, American Motorcyclist, up online. The archive spans from 1955 to 2007 (over 630 issues!) and is available through a partnership with Google Books.
The easy way is to go to http://books.google.com and search for American Motorcyclist. If you want a direct URL, though, try this giant link, which will start you at January 1955.
All issues are available for free and are available in full format, including ads and covers. The digitizing is excellent quality though you will have to zoom in to read many of the articles (unless you have spectacular eyes.) How great to read about the upcoming 1955 Daytona Beach Classic, and the ads! I think may favorite one is the full-pager that uses Annie Oakley to sell savings bonds. (The headline: “She shot the ashes off the Kaiser’s cigaret”.)
You can do searches of individual issues, of course, but doing full-archive searches is a little more tricky. I found appending “American Motorcyclist” to my search sort of worked, but in the experimental searches I ran I never felt like I was getting a realistic number of results. Do full-archive searches with caution.
That aspect of search is disappointing, but this archive is absolutely worth a look.