I have a disassembled piston port derbi motor, swing arm and rear wheel. Weld up some mounts to your AMF and you've got yourself a derbi.
This thing needs a crank and top end, not to mention assembly, maybe some seals, definitely some crank bearings. But, if you want a project that will potentially be the best bike ever, this is it.
$100 plus shipping.
please realize though, this will need parts and lots of work to complete. I'll get pics of what I have a little later.