From what I understand, you can't just work on ANY homebuilt. It has to be one that you built (51% or more), you attended some approved workshops for that model and you get a certificate authorizing you to work on that homebuilt only.
A lot of people think that but it's not the case. Unless the flight manual of the experimental aircraft prohibits owner maitenance (never heard of one, ever), the owner pilot can preform all of the maitenance on their experimental. HOWEVER, if you haven't built >51%, you can not perform the Anual inspection by yourself. That must be done by an A&P. No IA req'd though.
The EAA can spell it out better than me. They have all the proof (through the FARs) to support that on their website. In a nutshell, part 43 doesn't apply.
