Snow blower stalls when I unchoke it.

As a general question, do you have to lube, change oil or what ever to the pressure washer pump itself. If it is model specific, I can add details. It is a Generac, honda engine and an after market pump. It is a horizontal shaft engine, pump mounts to the back. (not under)

Hi all! Let me start first by saying I am new to engines and am just starting very slowly to understand how it all works together. Therefore please excuse if I am missing something obvious. Anyways, I have recently come into possession of a ride-on lawn mower with a Briggs and Stratton 11.5HP engine (I can look up the exact details if needed, but I assume this is more of a general engine related topic). The mower runs absolutely perfect given its age (10+ years) and I do not really have any troubles with it. The thing that puzzles me though is the part about the choke. If I understand it correctly then you need to choke the engine when starting from cold to allow more fuel and less air to get to the combustion chamber. Then once it runs, you slowly push the choke back in, providing more air into the mixture. Now the thing is, with my mower it seems to be the other way around. If I choke it, i.e. close the air intake, it does not start at all. If the choke is completely open it starts immediately and runs very strongly. Also if I try (just for testing) to choke it after it has already started, the engine dies or becomes very weak. I also verified that the air intake really gets restricted once I pull the choke by looking under the air filter. The filter itself is clean and saturated with oil - therefore looks fine to me. Technically I do not really have a problem with the setup, as it runs fine, but I assume that this might lead to a problem in the long run as clearly something is not as it should be? Can someone explain to me if I need to worry about it? Thanks