For sure change the plugs, oil and if the bike has sat for any length of time, bleed out the brakes and clutch fluids.
I would consider progressive front springs and a Condor Brace and the handling will be amazing.
(Super brace but made by our own Condor)
No get up and go? SOMETHINGS NOT RIGHT!!! These things move!
Probably only running on 3 cyl. They run surprising well on only 3.
When you start it up, feel the pipes (don't wait too long or you'll burn!)
A cooler pipe will indicate the one not firing.
You may need to do some carb cleaning.
SEAFOAM!!!!! (at the least!)
You may want to check the neck bearings while you have it stripped down....and inspect the frame....83's are known to crack at the back
If you do have a 2 brush starter, you can do a ground mod (by Dingy I think)
And upgrade the battery cables to 4 gauge. (or just go to 4 brush)
Have you done the battery warning bypass? If you have a gel or glass mat battery you will will need to do that to eliminate the flashing red warning light and battery icon.
You should pull the back wheel and grease the splines, and check the brakes while you are at it.
Have fun! These are great bikes!
The TCI is unique to 83...but Dingy had done a replacement group buy if yours goes south.