I wonder if trouble with vacuum petcocks was a production lot issue. My left side petcock went leaky while the bike was still under warranty in 1979. I didn't replace the other side until 2003. No problems since. Generally I drain the tank if it's going sit for a prolonged period. I agree with 5t , I like the vacuum controls. But when one fails beware, when #2 failed I had just filled up for a long Texas middle of nowhere ride and smelled gas then saw it flooding out of the breather box. I was lucky i was close to the barn.