Are you and your neighbor friendly? No negativity, no animosity?
Yes?
You want it to stay that way?
Yes?
Then I would say no, don't rent it to him. Way too much liability. What happens if he crashes it? What happens if he crashes it, gets hurt super bad and decides to sue you because the crash was somehow your fault? What if he accidentally kills someone and they both(renter & victims family) blame it on you for something wrong with the bike that you should have taken care of before loaning it out? Just way too many what if's in this sue happy society nowadays.
I would just say sorry, can't do it and point him towards twisted road, eagle rider or riders share.