Question, I have a 2000 400EX which recently had the head gasket replaced on it. We noticed that the head nuts were loose when we replaced the gasket. After replacing the gasket the nuts were torqued down to spec and everything was fine for a few weeks until we noticed oil leaking between the head and cylinder and found that the nuts had loosened up. We torqued them down and a few weeks went by and again the nuts loosened up. Would anyone know what to do about this problem? We did not replace the cylinder or studs. Is lock tight needed or is a locking type nut needed? Thanks in advance.