It's a great idea but a very ambitious project..
Few people have the writing skill and many have opposing opinions. Someone will have to wade through it all.
Voluntary or not, if somewhere down the line there's money involved the question of who owns the information will come up on an international copyright level. The publisher (you) better know what he's doing.
The framework might be hundreds of questions.. People who are familiar with that bike can answer questions voluntarily. This sounds an awful lot like what happens in these MA forums.
In fact, the archives here are what you can expect to get when people begin to contribute. As an experiment, gather some info from the archives on one specific topic/brand/model of bike and try to edit it into some readable book format.
But if you have ideas about actually using or selling the info in the archives maybe you should first check with whoever owns MA or with an attorney..