XR650R or XR400R into a street legal bike. Anyone do this?

Sure...

Talk to Scott, his website is www.scott-world.com/xr650r/

Only two-strokes cannot be converted to street use, since they won't pass the emissions standards. You should be okay because both the xr650r and xr400r are four-strokes.

Xr400r Street Legal

Laws do differ state by state. Ask if the following is on the title "For Off Road Use Only" or words to that effect. In a lot of states, that makes it just about impossible to title for street use. I know riders with the Big Red Pig (XR650R) that have successfully titled and plated the beast.

Another source is the Adventure Riders website.

See below.

Also a source for a used machine and advise on modifications that work and ones that don't work.

FYI, if I were choosing, I would look for an XR650R verses the XR650L. Better machine to work with.

What you neglected to say is what does this buyer want? A broken fender does not make a bike illegal to sell. it probably was "open and obvious". You should have noted your sale invoice "as is where is - no warranty". if you didn't - too bad. the dam thing is 17 years old for heavens sake. Does he have "proof" that the DMV (or whatever you call it) will not issue a license? Maybe he is just having "buyer's remorse" and it is simpler for you to take back the bike and sell it to someone else - so this guy doesn't come after you with a chain saw some dark night.

Not a recommended course of action-get an XL-they're BUILT street legal.

Laws differ by State, better check before investing any $$ into a project that can't be finished.