I'm about at my wits ends trying to get the proportion valve on my 71 Demon to stop leaking. I purchased a new one from Classic Industries and it leaked where the octagon shaped fitting screws into the housing. Snugged it still leaks. I ordered another through Summit and same problem. Leaks at the octagon shaped fitting. I'm about at the conclusion that these re- pops are nothing but Chinese junk. Has anyone else had these issues?