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.
Just to clarify, absolutely anyone can work on an experimental--it doesn't need to be an owner/operator or a pilot or an A&P or an IA--absolutely anyone could do anything to it. See my earlier post about 51% and repairman certificates.
