Hi Steve I too live in Tennessee. Here is our laws if you want to build legal.
Tennessee law 55-8-101 (35):
(35) Motorized bicycle means a vehicle with two (2) or three (3) wheels, an automatic transmission, and a motor with a cylinder capacity not exceeding fifty cubic centimeters (50cc) which produces no more than two (2) brake horsepower and is capable of propelling the vehicle at a maximum design speed of no more than thirty miles per hour (30 mph) on level ground. The operator of a motorized bicycle must be in possession of a valid operator's or chauffeur's license, and shall be subject to all applicable and practical rules of the road. A motorized bicycle may not be operated on a highway of the interstate and defense highway system, any similar limited access multilane divided highway, or upon sidewalks;
Staton Inc and EZ Motorbikes both have good kits which are legal here. Granted if you obey the traffic laws, don't endanger others or be a public nuisance the cops probably won't bother you. In 2005 my x brother-in-law ran into my brother. Both were hurt really bad and had to go to the hospital. They both got charged with operating an improper vehicle on the public roadways. This happened in Knox county. In court the judge said the bikes were improper due to being over 50 cc and having a manual clutch.
This is the main reason I build legal now. What happened to my brother inspired me to build a bike which could shift multiple gears automatically. I currently have the only motorized bicycle in the world which shifts 5 gears automatically.
I wish you well in your build and maybe we can ride together some day. I'd like to make a video of several of us riding around the track at Bristol during Speedway In Lights around Christmas time.
