See newly revised (May 2012) http://www.txdps.state.tx.us/msb/documents/VDRchart.pdf which clearly states the difference between a Moped and a Motorcycle as defined by the State of Texas.
Also, http://www.statutes.legis.state.tx.us/docs/TN/htm/TN.551.htm for supporting info.
So, if you...