Benjamin 312 pump cup ajustment

[Jspeak]

What is behind the vent hole is just a cup holder and cup that's it only maybe 1/2 or 9/16 total length.

[Jspeak]

Think I am probably going to get the pump rod off ebay with the felt oilers on either end. Thanks for all of the input.

[Rob112o]

It's definitely not the original. That's why you can't get it to just the right area. As you can see in my one pic my, cup fully passes the air hole. Can't tell if yours does or not with the pic you provided. You can either get an original or try and get one from a vendor or have someone make one. Another option is to drill hole longer so it gets a full gasp of air.

[Jspeak]

You can't really tell in the pic but in that position th cup is clearing the air hole. Here's how she looks after the brass black.

[Hoosier Daddy]

That is one of the first, if not only, photo I have seen of the results from Brass Black.
Thank you!

[Jspeak]

Just to update progress, I was having trouble seeing how different pump rod would help when it seemed stroke was the problem. I found that with the pump all the way open I could push the piston open with my finger another 3/16 to 1/4. The stroke length that I was loosing seems to be coming from slack in the rivet connection in the pump arm. I believe repairing that connection to take out the slack will be the solution. Thanks again for all the input.

[Hoosier Daddy]

Ah-Haaa!
That'll certainly do it. Hopefully it's just the pin worn and not the holes in the linkage wallowed out.

[Rob112o]

Like Scott said good chance the pin is bent at the piston guide off of the link lever (from over pumpers). You shouldn't need to think if it was the rivet which you are describing. It should easily visible the added movement. It can be the link lever is bored out of the rivet is worn. My guess is it's going to be the link lever has been bored out by the rivet. Caused by over pumping and no lube being out there over years.