Question about Craftsman 20 hp 42 in. Deck Lawn Tractor - CA Model
The needle and seat in the carb is not seating when the float level is high / float bowl full.
This is from the B & S Carb service manual:
An engine that exhibits leakage after it sits for a period of time can be caused by a number of problems. The most common of these is dirt. Any imperfection on a needle or seat surface, such as a small particle of dirt, can cause an engine to perform well in all other scenarios but still leak after sitting a period of time. In addition to dirt, an improperly vented fuel cap can allow pressure to build in the tank which could overcome the float assembly and result in a sporadic leak.
When an engine is not in use, the fuel in the bowl is exposed to the atmosphere via the bowl vent. Fine
particles of dirt or debris that normally would be suspended in the fuel and pass completely through the carburetor, settle out and end up at the lowest point between the fuel inlet fitting and the inlet needle. As the fuel slowly evaporates, the float responds by lifting the inlet needle very slightly off its seat. The dirt present moves in and lodges itself between the needle and seat. Now a slow but steady flow continues into the bowl, eventually showing up as a static leak.
These are the 2 most common causes of carb overflows.
Before replacing any parts attempt to clen the needle and seat area first by removing the float pin and dropping the float down so that any debris can be flushed out.
A new needle and seat is cheap and can be purchased at every lawn mower repair and parts supply. If you do change the needle valve make sure to tke the extra step of removing the old seat and replacing it. The rubber seat gets hard and the leaking overnight symptom can manifest itself again sooner than you might expect.
MAKE SURE YOU HAVE YOUR ENGINE MODEL NUMBER WHEN PURCHASING PARTS
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Posted on Aug 28, 2010
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Posted on Jan 02, 2017
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