clicking into first while running and sitting still makes a loud bang and the bike nugges foward, and its not fully engaging either, when i shift at full throttle and high rpm its letting the clutch slip, could the clutch be bad in a bike with 4,205 miles on it? I think im just not adjusting it right. What affect does the adjusting nut about the side cover have?
Probably all of the above.
It is a wet clutch and spring pressure keeps it engaged. A long time of sitting may have squeezed out the oil that normally swells the friction plates. There are many friction plates and when they lose their thickness, the clutch slips as the springs run out of travel and pressure on the clutch pack.
If you haven't glazed them by slipping too much. A good soak in oil might help them recover.
Something, you might try is letting it sit over night with the clutch pulled in (cable tie, rope, etc). This might allow the oil to soak back into the friction disks and allow them to swell up again. It would be helpfull to spin the clutch in the oil bath, too. By turning the rear wheel in gear occasionally, so a different section of the clutch disks are coated with oil. The alternative is to take them out and soak them or replace them with new disks that were soaked over night.
Wet clutches are sensitive to the oil used, too. "Energy conserving" oils are a no no. If you used that, then your clutch is ruined. What oil do you have in the bike?
I will warn you that a dragging clutch will bend shift forks and damage gear dogs inside the trans. Jerking into gear, as you describe, will soon destroy the trans.
If you can't get the clutch adjusted so it will not drag, you may have a grooved or worn clutch actuating rod. Better take that out and examine it. If I recall, there is a ball at the clutch side that can wear out. May have to take the clutch off to get to it, but the end of the actuating rod will look funny if that's a problem. Post a pic if you're not sure.
The adjust nut on the side cover (actually a screw slot) determines how close the actuator is to the actuator rod. And thus, where the clutch lever engages. The lock down claw or fork you lost and bolt lock that adjuster in place after you have removed the slack from the lever.
There is another cable adjustment at the lever, too, which should be adjusted for minimal showing threads, before making adjustments at the cover slot and cable end at the engine unit.
Cheers,