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


QUESTION: I have a B&S 18hp ohv Intek single engine that I just overhauled the carb on because it was leaking gas into the crankcase and causing tons of white smoke. When I overhauled the carb with a 697241 kit it came with two different needle valve seats. I installed the one with the larger hole. I installed the carb back onto the engine and tried to start it only to find out my battery was dead so I put it on charge, came back about an hour later and saw that the carb was flooded looking through the intake where it connects to the filter shroud. What did I do wrong? Oh, I checked the fuel solenoid and it works fine.

ANSWER: Did you verify the float height?  If the float is plastic it is not adjustable but if the incorrect seat in installed you will notice the float height will be too low causing the carb to flood.

Was there a groove on one side of the inlet needle valve seat?  There should have been and the groove should have been placed down, away from the needle.

All of the techs as the shop use one of these to verify the carb is not leaking:

They do this after the rebuild, before they re-install and after they have installed the carb and test ran the engine.  It's a little pricey for home use but it is a must for verifying carb inlet needles/seats are not leaking.

Last question, was the new seat you installed the same color as the old seat?

Let me know.

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QUESTION: The float seems to sit level if that's how it is suppose to sit. There are no grooves on either seat, just tapers at the bottom where the hole is and they are also made of brass just like the original. I hope this helps. While waiting for your answer, I also tested the fuel shutoff solenoid and it also works so it's not that either.

ANSWER: The float height should be close enough...they usually sit level or near level with the carb flipped upside down.

What is the engine model and type number?  I'd like to look to see which seat(s) are offered for the carb.


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QUESTION: The carb kit # 697241
The Engine model #31H777 & Type# 0210E1

I assumed there were 2 carbs offered for your engine.  Based on the carb kit number you must have the Walbro LMT series carburetor.  Is this correct?  If so, the carburetor uses a brass/steel inlet needle seat and the inlet needle has a viton (rubber) tip which is supposed to stop the gas when the float bowl is full.

Did you replace the inlet needle seat and inlet needle?  99% of the time just the needle needs to be replaced.  Replacing the inlet needle seat takes some practice...see page 78 of the URL below:

When we rebuild/clean carbs we also flush the entire fuel system by draining all the fuel from the gas tank, usually removing the fuel tank and then blowing compressed air to ensure there is no dirt in the fuel tank.  All the lines are either removed and air blown through them or replaced.  We always replace the fuel filter.  This may be a little more work but we need to make sure there is no dirt in the fuel system...or it could cause the carb to leak.

Let me know if you replaced the just the inlet needle or both the needle and seat.


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Eric A. Jones


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.


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.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

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