well i recently bought an 84 GS and ive noticed there is an oil comming from the back of the motor, it leaks through the fly wheel/clutch area. my question is could it be the rear main seal or something else?

 

It is likely the rear seal. Not difficult to replace once you pull the tranny,clutch and flywheel. You may as well replace the clutch, T/O and pilot bearings and resurface the flywheel if it needs it. Good time to check the front main bearing on the tranny also.
Todd