Carburetor loses prime after 8+ hours

You have not been able to buy the chlorinated "stuff" for some time now. The major content of chlorinated cleaner, "tric" or trichlorethylene, and it is NOT flammable. It is true that chlorinated solvents (if that is what you have) produce poisonous phosgene gas (Can you spell Hitler?)

I guess the "new" stuff is mostly petroleum products, and it will burn.