Looks like you found a vaccum pump. GTG. You are very lucky

But incase it doesn't work out or someone else needs a replacement fuel pump for the K161/K181 I'll list the part#, supplier and price I gave for a direct replacement mechanical fuel pump. It is plastic but the one I ordered included several adapter fittings which worked out fine.
FYI, there are over 700 spec's/variations of the K181 alone and it used at least 3 different fuel pump variations. I discovered this after much research when my vaccum fuel pump leaked more than it pumped on my 876.
In any case the part # is: 41-559-02 (or 4155902) and the price was $32.12
I got it from Tulsa Engine Warehouse and they're on the web and list on ebay.
It was a direct boltup and works great, and they're not manufacturer discontinued