considering you just put the motor back together, did you ride it long enough for it to get all nice and fueled up?
i got my complete re-build done today, and it took me two blocks to start it, then it sputtered around for the first mile or so.
mostly because i dumped 2 capfuls of oil on top of the piston when i finished building it to make sure it wouldn't be a "dry start."
mine runs great now.
i did have to adjust the flower nut again when i got it all installed. with the clutch cable hooked up, the wheel would roll without the lever pulled in, so i tightened it up.
is your clutch adjusted right?