85 gs runs ok if below 1/4 tank but bad if over dirty tank ?
 

so i picked up an 85 gs with 104k miles about a month ago

all stock except a jank fuel pump wire alongside the door jam as far as i know

im using 1oz per gallon of ethanol stabilizing 2 stroke oil and 87 octane on this tank of gas

it generally runs like crap and is has moments of good smooth power

it idles after being fully warmed up sometimes

after driving it for about 30 minutes it stalls and when i turn the key the fuel pump doesnt power on until it cools off

so i am going to replace the pump and rewire it ( as of now i believe its either powered or relayed off of one of the ignition coils ) along with the filters soon

but today i noticed when i started it that the tank was really low but the idle was 99% more stable and it didnt miss hardly as bad

why would it run so much better low on gas ?

I think it running better lower on gas is just dumbstruck luck. everything your mentioning is a dirty fuel tank, dirty fuel filter, dirty carb, or all of the above. May even be your fuel pump since it sounds like its overheating and not pumping fuel, but, since you mention a janked wire, tells me someone has tried messing with it before, and may not be heavy enough wire to power the fuel pump, or bad ground