Mower not idling well

[jasonscheltus]

I managed to get this mower running again, carb clean, fuel tank clean, and a new spark plug.

But it's not idling or revving very well, it's like the fan blades are blowing on the plastic arm thing too strongly, causing it the throttle the fuel off.

I made a video, you can hear the engine slows and speeds up by itself, and seems like it's doing too much! https://youtube.com/shorts/mla5BsjMxMc

Would love any help!

 

[bertsmobile1]

Well it is still surging so either the carb is not supplying enough fuel or there is an air leak between the carb & the inlet valve.
On those B & S engines the O ring the carb bolts up to wears, goes hard or just leaks
The manifold it sits on has a tendency to crack on the under side where yo can not see it and on rare occasions the screws can come loose or the gasket fail
I replace about 15 to 20 of the manifold tubes annually and that reminds to add some to my pre-season order

Other than that the long pick up tube that goes into the fuel tank can split lengthwise or where it enters the carb body
It also has a screen that is subject to clogging
The diaphragm & gasket under the carb have a finite life and they are easily displaced unless you assemble the tank to the carb upside down ( Drop the tank onto the carb )
The main jet under the slip of mesh screen rarely clogs but it should be checked
When assembled the actual torque on the 5 screws is not all that important, but they must be all the same or the gasket will leak.
When it was apart the top of the tank must be checked for flatness as it is prone to warping .

 

[Tiger Small Engine]

Well it is still surging so either the carb is not supplying enough fuel or there is an air leak between the carb & the inlet valve.
On those B & S engines the O ring the carb bolts up to wears, goes hard or just leaks
The manifold it sits on has a tendency to crack on the under side where yo can not see it and on rare occasions the screws can come loose or the gasket fail
I replace about 15 to 20 of the manifold tubes annually and that reminds to add some to my pre-season order

Other than that the long pick up tube that goes into the fuel tank can split lengthwise or where it enters the carb body
It also has a screen that is subject to clogging
The diaphragm & gasket under the carb have a finite life and they are easily displaced unless you assemble the tank to the carb upside down ( Drop the tank onto the carb )
The main jet under the slip of mesh screen rarely clogs but it should be checked
When assembled the actual torque on the 5 screws is not all that important, but they must be all the same or the gasket will leak.
When it was apart the top of the tank must be checked for flatness as it is prone to warping .

So basically there is a lot going on with the carburetor being right for it to run right. To set RPMs at desired speed, you need a tachometer and bent the tang at far right that long spring connects to. Around 3250 RPM on most engines is good, 3600 is max.