Honda600rr
XS650 Member
hi I know this is an old post.i have a yamaha xs400. bought as a project bike.this bike is driving me nuts carbs on carbs off .lol.had the bike running pretty well but I has changed these o rings and thinking that they are not resistant to fuel and are starting to dissolve. Noticed black residue in the float bowl.i havnt removed the valves yet to check. but has anyone else had this problem. the bike won't start now .If the O-ring doesn't seal, the float valve can't control fuel level. Does that answer your question?