Tanaka 870 Pump Not Locking

[danr]

I recently disassembled, and reassembled my Tanaka 870. (I was changing the pump fore-arm thing).

 

After reassembly, the pump no longer locks in place. Normally, it should lock in the forward position after you rack it, but it doesn't do this anymore.

 

I was wondering if any of you could help me diagnose what the exact problem is, and how to fix it.

 

Also, I'm not sure if this is related, but I found an extra bit laying about while I was reassembling the m870. Its a little pin on a spring, sort of like the thing you would find in a safety, that allows it to click into place. However, I'm not sure if this is from the Tanaka, or just something laying about from a previous project, that I just didn't notice.

 

Any help would be greatly appreciated.

 

Thank you very much.