Many just opt to not run the tank.
If you don't overheat on the regular, you'll be fine without it. It'll puke out and not recover though.
But plugging the hose from the radiator would be a bad idea.
Here's my '95 that I did up in '96 and haven't changed anything since. It's been in and out of style like 3 times now. I suppose it would now qualify as "old school" I know I do. LOL
Cable off
Torque 6 pressure plate bolts
Adjust center adjuster while holding the actuator inboard with your other hand until arrows line up.
When you release it it will spring outboard. That all the freehand movement it will have. You can't overcome the 6 clutch springs by hand.
At this point you can close up the side case.
install cable with and adjust with a little slack at the handlebar adjuster.
Your original post is a little hard to follow. So the clutch is slipping and didn't grab at all?
You can't push the actuator by hand when it's all together anyway, So don't know what you mean by that.
Hard to believe it worked one day and not the next, but it does happen.
Did you Ohm test all 3 things? lighting, running and pick up?
Take the side cover off and visually inspect? Look for broken wires, Ohm test directly on the stator.
Yes, one of each jet in each carb.
After an extensive 3 second google search....
https://jetsrus.com/a_jet_kit_atv/yamaha_350_YFZ350_banshee_1987-2006.htm
Knocking a orange or black coil wire off is common.
Key switch jumper (if no switch)
Accidentally plugging in the TORS box ( when the system is deleted)
A broken wire at a pin (on a connection recently unplugged/plugged in)