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Hey guys, bought an old green sears craftsman 24" snowblower with the OHV 250 cc 1150 snow series engine. Engine code is 15c114 1485 e8 and the snowblower model number is 944.529204.
It is running great but popping from time to time...I want to change the plug. It now has the Champion RC12YC in it and it maybe the wrong plug for this motor as it is all fouled. I checked the gap and it was set near .040".....
What spark plug should i use and what is the spark plug gap? .020" or .030" or .040"?

Unfortunately, I cannot find the Owners manual online...
Thank You!
 

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The gap is usually around .028-.032" in that area. A lot of the popping can be caused by a "lean" fuel condition.
If it is popping at full throttle while it is not under a load, thats a lean condition. The engine will actually only be taking fuel from the low speed jet then with no load.
Once there is a load on the engine, the throttle plate opens further and then the fuel comes from the main circuit, which is richer.
Plug fouling can be caused by many things, too light oil viscosity, oil contaminated and thinned by gasoline contamination. That happens with a leaking float, the needle and seat could be worn, allowing the fuel level to be too high in the bowl, causing a rich condition, a fouled spark plug, requiring either cleaning or replacement, an ignition problem, a coil or plug wire/cap. It can be many things.
Also your valve clearance could be out of adjustment, check that also.
You might want to go with an RC17YC, a hotter plug, the 12 is a little cool for wintertime operation.
Sometimes the needle seat expands or becomes swollen in certain carbs, usually caused by ethanol, and that can cause a low fuel level in the bowl, causing a lean condition under a load, then the engine will act like it is running out of gas momentarily until it recovers by the float letting more fuel into the bowl. You will notice a periodic "surge" when that happens.
 
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