I have one broken sub-valve (RHS) and one stripped sub-valve (LHS) from my 1990 KDX 200 and from what I understand I'm not the first to have this exact same scenario. (e.g. Buckhat) Does anyone know why these parts fail so readily? Do you think steel ones would be more reliable? Are there any steel ones made out there? The bike's only got 150 easy hours on it since the last top-end was done. :|