Go to the first post in this thread and look at the photo. At the top of the photo, you can see the needle inserted into it's opening. Note the shoulder on the needle where the fork pushes on the needle and the surrounding housing (a slight casting ridge there) are at about the same level. When the fork is in place it can't fully depress the needle as it also contacts the surrounding housing. In a normal situation, the fork would contact only the needle and there should be visible clearance between the housing and the fork. The first post explains how this was resolved. If additional questions, please let me know.

Edit: I cleaned up the housing by removing a bit of metal from the needle opening with a ball end mill turned with my finders. I stated in an earlier post that a 3/16" or so tool would work but realized mine was closer to 1/4" or 5/16". Even a good sharp drill bit would do the job and again just hand turned.