First thing to check is the gap at idle. Look into the carb and adjust the gap to about 1mm.

Reset the HSN and LSN to base settings and start over on tuning.
LSN flush with collarand HSN 2-2.5 turns out. Adjust in 1/8 increment turns.

Drive train lock up could be the drive cups have come loose and need to be reseated on the flat side of the shafts. Also apply locktie to the grub screws on the cups.
the cup with the disk brake on it needs to be installed so the cup goes through the disk itself.

You can also try video help files

www.rctoysnh.com/catalog/videohelp.php