There is a fuel pump. When this problem started back in the fall it went from running great to where it is now in an afternoon. Right after I ran out of gas. I do a lot of mulching and it gets pretty dusty. I remember tearing the cowl off and checking for anything obvious. Blew it clean with an air gun much like I do after every use. When we have a break in the daily snow fall I'll get into the carb. I'm a little apprehensive about tearing it apart right now as I'm relying on it to plow the driveway and paths. I screw up the carb somehow and I'm shoveling. Thanks to all for the help.
Mummmm, very dusty mulching you say, puts a little different slant on things.
Two more things come to mind.
1) crud in the bottom og the fuel tank restricting the supply of fuel
2) crud stuck in the fuel pump air filter reducing its pumping capacity.
Once again you are looking at bypassing the items in question .
To do this you will need some sort of temporary fuel tank and some fuel line if you do it relatively quickly then you can use simple PVC tube just make sure it does not contact anything hot enough to melt it.
There will be enough fuel in a walk behing mower fuel tank to do both of these two test and by the sounds of it you won't be needing the small mower for quite a bit.
First test is to hook up empoary tank to fuel pump and run for about 10 minutes, problem goes away then you ar looking at crud blocking the fuel tank outlet or fuel line between tank & pump.
Second test will require you to hang the temporary fuel tank above the engine so it will gravity feed.
Plum it directly into the carby and try again.
If neither make any difference then you have at least eliminated two lines of enquiry.
Usually a low fuel situation causes the engine to hunt so the revs rise & fall and this will even out a lot by engaging the choke slightly and the engine will run fine with the choke fully off & the throttle stopped down to idle.
Usually an air leak will cause the engine to run faster than it should due to lean burning at large throttle openings and at idle it won't run at all.
