HI,
I am fixing a Toro Super Recycler (20043) for a friend. It's has a 6hp
Briggs engine. It has no throttle (auto throttle?). I have replaced
the plug, fuel line, and air filter. I also rebuilt the carb including
new gaskets. I cannot get the mower to start. If I add a few drops of
gas into the cylinder then it starts right up and runs like a champ. I
can even shut the mower down and it will start right up again. But if
you let it sit for a day, it will not start again.

Its a primer system but its an odd setup as the primer bulb is on the
air filter.

The throttle / governor seems odd to me also. A spring pulls in one
direction holding the throttle open while a air vane on the engine
pulls the throttle closed. So while running the throttle is in
equilibrium between the two. The odd thing about the setup is that
when you are starting the engine, the throttle is wide open.

Any suggestions?

Thanks in advance.