If it idles low and slow (however you get it there), the air/fuel mix appears to be correct. In addition to the idle air/fuel mix (the needle), there is also a throttle idle stop. On the ’84, the throttle stop is the wheel on the throttle side of the engine down at the pan. They are often broken by a prior owner, but try it — simply sets the throttle at a lower/higher idle speed. It sounds like yours needs to be adjusted. The best approach is probably to adjust it to its slowest position, then just use the twist grip to throttle up to high idle (in neutral) for starting. The markings on the twist grip are pretty much just for general reference. Just turn the twist grip counter clockwise as far as it will go with the gearshift in neutral (should give you a high idle setting).
The link and sync simply involves adjusting the throttle wheel to first nudge the cam on the mag plate (timing plate) at the mark on the cam. The wheel should first begin to open the carb throttle plate at that point. Bottom line — twisting the grip opens the carb at just the right timing point. You will have to remove the manual starter assembly for access.
