https://www.automd.com/recall/campaign_c66157/ I remember seeing this a long time ago so I dug it up just so people can see it. This is why the xs400 petcock was changed in 1980 to a different style. I know there have been a few guys that have posted pics of strange looking diaphragms and blocks in them. They must be the old ones. The recall was for 78-79 models but I think the xs360 and the 77 xs400 had the same. I doubt yamaha will give you a new one