WD-40 residue will gum up the works at some point. Use Tri-Flow - bicycle shops carry it and you can get it mail order. It is expensive but worth every penny. You have to remember to shake the stuff though. It will free up the tight screws. Yesterday when I was working on the clone I had stuck throat plate screws. I put a little Tri-Flow on it and kept oiling the rest of the machine. Then I tried the screws again and they turned just fine. Same on the balance wheel. It was stuck but good - T-F got it loose. It seems to cut the dried up oil just fine and does no other damage. You do not need a big bottle and you do not need spray - just get a little drip bottle.