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I unpacked my mower after moving across the country and noticed an issue when trying to run it. It seems to run ok but idles with a wavering sound and eventually shuts down, I then need to give it some time before I can start it again.

Any ideas what it could be?

Here is a video of the the issue.

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Pull the carburetor and disassemble carefully, clean it and the main and idle jet passages with carb cleaner in a spray can.

More than likely bowl sediment go knocked loose in the move and is now partially clogging the idle jet.

What I think is happening, the engine tries to idle on the idle jet but it is not getting enough fuel to maintain the idle, when the rpm drops too low the rpm governor opens the throttle a bit, then rpm rises and the governor backs off to let it idle again, then the cycle continues.

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I don't disagree with @Moab.

I would add, that sure sounds like a positive feedback on the air vane that controls the idle speed. The air vane is driven by the flywheel vanes. If the vane gets bent, or a spring gets disconnected, the whole thing goes in this fast slow oscillating control loop. If you remove the cover you should be able to see the control vane. Look for a spring attached to that large metal plate that is only connected at one end (etc...) Basically the throttle plate at the carburetor is opening and closing way too fast on its own, without control from the operator speed cable.

And while you are cleaning up the carburetor (per the excellent Moab answer) do check the inlet screen at the bottom of the fuel pick up. You should easily be able to blow air thru the pickup tube. I've seen those screens getting clogged easily...

  • Some use an internal governor in the crankcase, but is a good answer I did not think of. – Moab May 16 '16 at 19:02

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