My old Fuji Marlboro Folding bike DOES fold but going from unfolded to folding when it's about 75% folded it gets really tough and really requires some muscle. Of course when trying to unfold it also requires some muscle to get it open again. I read that some penetrating oil may do the trick but I have some questions.

1. Where do I actually put the penetrating oil? Do I lay the bike on its side and spray the PO right onto the outside of the frame onto the hinges and let it seep in to the hinges? Do I lay the bike up side down and spray directly into the frame tube where the triangular "bash guard thing" is (for the bottom hinge)?

2. Assuming the PO works and I get the frame to open and close easily again, how do I properly keep it lubricated? My understanding is that PO will not only clean out rust and gunk but will also clean out any lubricant as well. I don't want to end up back in the same place again later on.

Any help will be appreciated. Thanks.

I'd first make sure there's no outside of the folding mech. issues. Like a cable that's binding/hindering the folding movement. I would add lube to the hinge directly. Placing the bike in whatever position that makes it easiest to access the hinge. Don't forget to lube the latch or clip device too. It may take some cycling through the folding action to have the lube fully penetrate the hinge. Once a thin lube does get in then follow up with a thicker lube. Periodic lubing will keep the hinge from getting tight in the future. Just like one's car needs the oil changed even without much use over time so too a bike needs periodic maintenance. Andy.

I suggest you post your questions to the Folding Bikes Sub-Forum. It is very active with enthusiasts. Good Luck