I have never heard of a bike week at WDW. As far as "themed" weeks / weekends, there is Marathon Weekend (in January), Pop Warner (in December), all the Epcot International Festivals (basically every month of the year), Star Wars weekend (in May and June), MNSSHP (August - November), MVMCP (November - December), Christmas Week.
Easter and Christmas are times to avoid. Presidents Day week as there is always a twirl competition held at Disney, schools in the New England states have winter break and they flock to FL. and Daytona 500 race so you will see lots of race fans staying at Disney.