Can't see an external one. Perhaps inside the fuel tank?
The GCV160 motor on my leaf vacuum has suddenly started 'hunting,' quite badly,
#2
ILENGINE
Most push mower style engines have a molded in fuel filter inside the tank. The surging may not be directly related to the fuel filter in the tank. More likely old fuel residue or other things have made the fuel passages inside the carb partially clogged. Needs a good carb cleaning. Or in the case of most the GCV series just easier to replace the carb. And some of the carbs for the Honda GCV engine are under $20 for the OEM carb so don't even look at aftermarket Amazon or Ebay carbs.
I find it better to clean the carb than take a chance on an aftermarket that may be flawed. They are pretty easy to clean. I have a good success rate. The bowls and gaskets can be purchased separately if they are damaged beyond reasonable repair.
I recommend starting at the tank and verify if there is a pencil filter shoved into the end of the fuel line or the tank fuel nipple itself.
Surging is a sign of lack of fuel getting into the carburetor. The clogged fuel filter is literally "dripping" fuel past it and starving the motor of enough fuel.
The other possibility is the carburetor low speed air bleed is clogged with debris. It is pressed into the carburetor housing just below the base idle stop screw. Often times they just need to be cleaned out with a really fine wire and some carb spray.
