The tank on my 85ZN700 is rusty. When I bought it in 2009 with 1k miles on it, I sloshed the gas around and dumped it to get the rust particles out and put a filter in the line and I've never had a problem as far as I know with rust clogging up the carbs. They will clog up easily if it sits for a while but with a 700cc engine with 4 carbs the passages are really tiny and it doesn't take much sludge to plug something. I keep Gumout with PEA in the gas which helps this issue. My 2 cents.