The transmission on this 1983 R80ST is serial number Z 078854. According to Robert Fleischer’s article on transmissions, the range of transmission serial numbers in 1983 was from Z 074700 to Z 084299, so mine is the original transmission as it is within the range for 1983.
I removed the transmission after removing the battery and battery box, the rear drive, swing arm and monoshock, and the air box and the pulse air and crankcase rebreather components.
I found water in the transmission gear lube. The speedometer cable was missing and the hole in the bushing for the cable was plugged with some cloth. Since the bike was outside for awhile, water entered the transmission through the hole in the bushing.
Here is the documentation of how I do this work along with a short YouTube video summarizing the procedure.
VIDEO: 1983 R80ST Remove Transmission
I am ready to remove the engine. Before I do that I will remove the top end of the engine to reduce the weight.