But I did lol. The whole bottom solenoid can be screwed off. I realized I could have bought just that for $10 on Amazon.
Appears you may have misunderstood what Star Tech is saying.
There is a o ring
INSIDE the metal shell on the solenoid and you cannot replace just the o ring. the whole solenoid assembly has to be replaced.
To get an idea of such the whole metal outer shell with the terminal assembly when on the carb can be turned by hand with friction and the solenoid wire terminal can be relocated due to the o ring friction INSIDE the metal shell. Yours got old and the o ring failed.
Best to not twist on the metal shell itself when removing or it may start leaking if the solenoid is aged..
OEM replacement solenoids are kinda costly.
The anti back fire solenoid can usually be eliminated if the proper replacement bolt/stud is used to block the threaded hole in the carb bowl. You can find info about such on-line.