Small Engines (Lawn Mowers, etc.)/Carb question

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Caerb
Caerb  
Carb
Carb  
QUESTION: I have written to you before about this tiller my son has.  It is a Craftsman Model 917.292403 and uses a Model 134202 Type 1118-E1 Briggs motor.  The parts diagram I downloaded shows the carb part number to be 498298.  He bought this tiller used from an acquaintance. The problem was it would not stay running unless it was partially choked all the time.  So we cleaned it out, put in a new diaphragm to include the spring behind the diaphragm.  There is a brass screw that we removed from the side and made sure it was clear.  It had two pin holes directly opposite each other on the shaft and one that was drilled into the end of the shaft.  There was no needle point.  The two opposed holes were clear all the way through, and a wire inserted into the end could be seen through those holes.  The screw was in all the way when we took it out, so we put it back that way.  Now when it starts, it floods itself out every time. Removing the breather assembly, gas can be seen pooled into the breather assembly. I have attached some pictures which shows the screw I am talking about.  I think it connects in some way with the pick up tube for the bowl in the top of the tank. The parts diagram doesn't show this part.  What do you suppose could be wrong now?

ANSWER: The screw in the "Carb" picture, the picture with the gas cap, is the Valve-Idle Mixture screw.  There should be a point at the end of the screw.  The part number is Briggs and Stratton 691777
Valve-Idle Mixture.

You can tell if the screw if functioning if, when the engine is idling, you GENTLY turn the screw in and the engine starts to stall, sputter or die.  DO NOT screw it in all the way or you will ruin the needle.

Did you separate the gas tank from the carburetor? If not, I'd separate the tank and see how many gaskets there are...there may be 2 gaskets.  

Either way I would replace the carb to tank gasket(s) as the carb and tank can warp causing fuel to leak past which can flood the engine.

Eric

---------- FOLLOW-UP ----------

QUESTION: Thanks for responding.  Heavens only knows what was done to this tiller before my son purchased it used from an acquaintance.  The screw did not have a needle at the end.  Just a hole.  We decided to try just cleaning the passages and replacing the spring and diaphragm without taking off the carb from the tank.  My son gave up and bought a new one.  However, I would like to solve this problem for my own knowledge.  I learn something each time with help from folks like you.  I will take this screw out and send you a picture of it.  If you were to stick a wire through the opposing holes on the shaft and one up the hole at the end of the screw, they would form a cross.  And it was screwed down all the way when we first removed it.  That had to have been done before my son purchased it. Neither of us did it.  Thanks again.

Answer
Some of the flooding issues can be tricky on those carbs, especially the older style.  They used to warp, the carb a little and the tank a little where they bolt together.  This is why many used 2 gaskets.  We sometimes have to remove the fuel pick-up tubes from the carb and use a special flat stone, very flat, and sand the bottom of the carb.  This "trues" up the carb but you still have to use 2 gaskets.

Eric

Small Engines (Lawn Mowers, etc.)

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Eric A. Jones

Expertise

Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.

Experience

Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

Education/Credentials
MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

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