-Drained all the fuel, cleaned fuel lines, added fresh fuel?I have a Honda gcv160a and I cleaned the carburetor and replaced all the gaskets from the carb to the engine and new plug and the engine still surges when mowing.
-Drained all the fuel, cleaned fuel lines, added fresh fuel?
-Does it have a manual choke? If so, does the engine run smooth/steady when the choke is ON? If so, for sure sounds like gunk still in the carburetor.
-Was it surging before the repairs, and no change at all now?
-Is this an all-Honda mower, or a Honda engine on another brand?
Double-check all carb parts, rods, springs, etc. and ensure they are installed in the correct order, and the two long bolts are secure. A vacuum leak can cause surging issues.
When cleaning the carb, it can be hard to really do a proper job, especially without carb cleaner and compressed air. There's an excellent guide here with full instructions & detailed photos:
How to Clean a Honda Carburetor
Finally, it can often be faster/easier to just replace the carburetor. For many Honda GCV160 engines, a whole new carburetor is $14~$25 list price. To match a carburetor, need a number from you:
-If a 100% Honda mower, need the serial number off the back of the mower deck. It is in the form of MXXX-1234567.
-If only a Honda engine on a non-Honda mower, need the serial number off the side of the engine block. It is in a dot-matirx print pattern, hard to see, so get a flashlight. Look for a number in the form of GXXXX-1234567/