Bikes aren't ok in wilderness. They are too modern.
Not all wilderness is the same. The easy to designate areas were done decades ago for the most part. Now interest groups like off roaders and mining interests and vacation home developers, to name some, do not want wilderness and have a big effect on Congress. A road may go deep into the area with some old resorts along the way (Gunflint Trail in the Boundary Waters, for ex.) Exceptions for them are made in some legislation. Negotiations can take many years.
Buying inholdings (mining claims, ranches that were abandoned decades ago) is a good way to get money from the gov't or have access across the wilderness allowed. There's a guy in Colorado who has made a career out of representing people with old inholdings or buying them himself. The same has been done when national parks or monuments are being debated for creation or expansion.
Patented mining claims granted surface ownership (unpatented ones didn't) and the mine may have hardly been developed or was abandoned, and the owners may be divided amongst scores of family members by now, or the county may have taken it for unpaid taxes. Researching tax records and other county property records can uncover this information and if you are willing to learn it, take the time and raise a lot of dust in old books, you may find something that you can use to screw up the wilderness designation process and get paid to sell to the gov't.
For decades public lands authorities set aside even more acres for study as wilderness. Politics, competing interest groups and underfunding stalled the study process and now some want to make just about all the study areas nonwilderness. This is an ongoing battle.