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I just came into a 12hp Murray Yard King and am having issues with it surging nad backfiring. It has the Over Head Valve engine by Tecumseh OHSK120.

Here it is: http://i135.photobucket.com/albums/q134/kirc0047/DSCI0048-2.jpg

I can run it on 7/8 throttle sometimes without this issue, but have to have the choke on in order to keep it from pulsating and shutting off. Weird, this didn't seem to be happening a couple days ago before I got it (just bought it used), but since have done some work to it and wondering if something got changed somehow? It could have already had this issue though, and I just didn't discover it yet.

I had to fix the drive system (friction disk) and in doing so, I balanced the machine upright on it's auger housing without draining the oil. Could this have done something unintentional? i.e. the oil ran into places in the engine it shouldn't have? I've also added an in-line fuel shut-off valve - could this be restricting just enough gas (slightly smaller passage/opening that regular fuel line) to restrict full idle?

The carb is very clean. Took it off and cleaned it. Maybe I need to clean it more. Wasn't very dirty though. It doesn't have an adjustable fuel mixture screw at the bottom of the carb, it's the fixed kind, but cleaned all three passages in that THOROUGHLY.

Spark plug looks good.

I've heard you sometime have to soak/dunk the carb in carb cleaner, but this isn't an option with this carb because it has an internal component with the fuel jet that is plastic and hard to remove and would likely get eaten up by the carb cleaning solution.

Any ideas out their? I am at a loss. Thanks in advance for any attempts to help with this.
 

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I would say more likely carb than governor.
 

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I had a similar problem. Cleaned the carburetor and had same problem. I then cleaned the gas tank and fuel line out and it started running fine. I think it was crap in the tank and line clogging the carburetor back up. Don't forget to clean carb again after cleaning the tank and line. I added Seafoam to the tank just as an extra measure.
 

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Like they said above check the carb to make sure it is clean.
But you said it was already, still go back through your work and double double check use spray cleaner and go through all the ports, lines and like nelsontj said check the tank also, check you don't have a broken spring on your carb linkage also.
 

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I just came into a 12hp Murray Yard King and am having issues with it surging nad backfiring. It has the Over Head Valve engine by Tecumseh OHSK120.

Here it is: http://i135.photobucket.com/albums/q134/kirc0047/DSCI0048-2.jpg

... but have to have the choke on in order to keep it from pulsating and shutting off. ...
I've also added an in-line fuel shut-off valve - could this be restricting just enough gas (slightly smaller passage/opening that regular fuel line) to restrict full idle?

The carb is very clean. Took it off and cleaned it. Maybe I need to clean it more. Wasn't very dirty though. It doesn't have an adjustable fuel mixture screw at the bottom of the carb, it's the fixed kind, but cleaned all three passages in that THOROUGHLY.


QUOTE]

The symptoms you mention point to fuel starvation / lean contition. It is possible that you have restricted fuel flow by installing fuel shut off, if the valve is smaller than the fuel line. (unlikely, but possible) It doesn't take much to block tiny passages in the carb,thus, a thourough cleaning of the entire fuel system is the only way to be sure the fuel is getting to the combustion chamber unhindered. I use spray type carb cleaner and air to clean these carbs. so far, I've not had any troubles. good luck
 

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just wondering...........
when you hooked up the shut off,
the fuel line isnt " U " shaped in some way......i had a small engine that there was too much swoop or bend in & it would run better when i moved it around.before i finally got the line strait
something to consider even tho its a remote possibility
 
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