(Portland, OR)  --  A Portland man is scheduled to spend six years behind bars after he pleaded guilty to a hit-and-run that killed a bicyclist.  Kenneth Smith Britt Jr. entered the plea last month to manslaughter, hit-and-run, and driving under the influence of marijuana in the death of 38-year-old Martin Lee Greenough.  Authorities say Greenough had a flashing red light on the back of his bike when he was hit from behind.  Police say Smith slowed down and then drove on following the crash.