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Small Engines (Lawn Mowers, etc.)/gas leaking from exhaust and motor wont run


QUESTION: Hello Eric ...  I have a Murray Select 42 inch that I bought used with a briggs 17.5 I/C OHV motor # 274826 ... It ran fine when I checked it out during the time of purchase ... the next day I ran it for 20 minutes then the motor just quit ... I thought it may have been the gas filter so I went ahead and replaced that but then I had noticed that there was gas leaking from the exhaust while trying to start it ( It didn't start @ sounded similar to no spark ) ... I have read Johns response ( Needle Valve ) to a similar problem and was wondering if the same remedy could be applied to my situation ... Thank You for your consideration


ANSWER: Most likely it is the inlet needle valve.  Does the oil smell like gasoline or is it really thin?

If the oil smells or it thin you will need to change and re-fill with new oil.
What is the engine type and code number so I can look up your carburetor.


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QUESTION: Hello Eric ... Thanks for your quick response ... The oil on the dipstick does not smell like gas it just looks a little dirty and I will be changing it soon ... The family number is YBSXS. The other numbers are 5012 VP ... Can you offer me any instruction on how to do this repair ?  Once again Thank You for your help in this matter ....   Bill

ANSWER: Thanks for the additional information but you need to double check for a type and code number.  The type number will be 4 digits such as 1234 followed by a 2 alpha-digit number (trim number) and then the code number.  The code number is a long number.

Copy and paste this URL in your will help show how to locate numbers I need.


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QUESTION: Hello Eric ... I copied all the number stamped into the engine ... I did not notice that they were broken down by model ,trim etc. ...the numbers are as follows  31c707 0230 e1 031 0217a ... Hope you can decode this for me ... Can you also give me the part numbers to the needle valve and the orifice ...or if there is a rebuild kit ... Thanks for your help & Happy New Year to you


Thanks for the engine info.  Looking at the parts diagram there are 2 carb models offered on you engine; 1) Walbro LMT and 2)Nikki

The name, Walbro (LMT) or Nikke should be stamped on the carb but you will have to remove the air filter housing assembly to see the stamping on the carb...a flashlight helps to read the stamping.

LMT parts:
Briggs and Stratton 231855S, Valve-Float Needle, (Walbro)
Briggs and Stratton 697241, Kit-Carb Overhaul, (Walbro)

Nikki parts:
Briggs and Stratton 696136, Valve-Float Needle,(Nikki)
Briggs and Stratton 796184, Kit-Carb Overhaul, (Nikki Carburetor)

There are a few tests, mainly a leak down test, we like to perform after rebuilding carbs.  You don't have to do this but it lets us know the needle is not leaking.

The point is you may want to remove the carb and take it to you local shop for cleaning/rebuilding is you do not feel comfortable doing the job yourself.  It's not very difficult to clean the carb but you really need an air compressor, even a very small one will work, to blow clean air through all the carb holes to make sure they are clean.

You should also consider installing and inline fuel shut-off valve.  These are cheap and will guarantee the inlet needle will not leak because you are shutting off the fuel supply each time you are done using the mower.  I installed fuel shut-off valves on all my mowers with float style carbs.  After I'm done mowing I just close the valve and let the mower stop bu running the carb dry.

Let me know if this helps.

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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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