Well Sammy .... about that message to Dahon .... :-)
I could pass it on .... but with a 07 bike which was left in the rain and used a lot .... all the grease in the world applied at the factory will not be there no more ....
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Wd 40 is not the best but cant hurt either ... just get some real grease or oil after you get it working as WD 40 is NOT anything like that. It works great to loosen things up but has almost no long time lubricating values...

you can get any penetrating oil and liberally spary it on the hinge for a couple days in a row... bending the frame as far as it goes back and forth and after a while it should work .......
thor