Legality of home-built electric bike?
I'm using Radioactive_Legos' Flat Tracker as a reference http://www.instructables.com/id/48V-Electric-Flat-Tracker/

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http://en.wikipedia.org/wiki/Electric_bicycle_laws#New_Jersey
If you remove the pedals then you will be like this lady:
http://www.pressofatlanticcity.com/communities/upper_capemay/electric-bicycle-or-moped-woman-caught-between-ocean-city-police/article_d632c68e-5fe7-11e0-ba2c-001cc4c03286.html
If you go faster than 25mph, then you will be considered a moped, and need to be licensed.
I'm from GA, so specific laws will be different. Our guidelines for not needing registration tag, etc. are:
-Engine displacement < 50cc
-Maximum speed goverened < 35 mph
And then, it has to have the usual:
-turn signals
-lights
-horn (that can be heard to something like 50 yards)
Lastly, from my understanding, the process is going to go: 1)Tax office for categorization (motorcycle, bicycle, custom uncategorized) 2) DMV/DOT safety inspection (note, it cannot be ridden to the inspection site, it must be towed or trailered [or pickup-ed...]) Even then, you might run into problems with not being a licensed builder, etc. My suggestion, find a small satellite office where you can chat-up a bored clerk who knows the right procedure and troll some bike-builder forums for info on your state.
I'm running into the same issues regarding building a hybrid tilting trike from an old motorcycle...