Small Engines (Lawn Mowers, etc.)/Toro S-140 Model 38100


This unit I have had for over 25 year and every year it started up on the first couple of pulls. For some reason this year it is very hard to start. I will take 20 or 30 hard pulls to start even when I ran it and shut it off for just a few minutes. I have new spark plug and fresh fuel with proper mixture.

S140 14" 1979-1981
Tecumseh engine: model AH520
Engine Type number:  Depends on serial number of blower unit
Mix ratio: 32:1
Max RPM:  4100-4500
Spark Plug:  Champion RJ18YC
Spark Plug gap:  0.035

Snowblower service manual URL:

Engine service manual URL:

When was the last time the carburetor was rebuilt?  According the parts diagram, you have a Tecumseh engine with a diaphragm type carburetor.  The metering diaphragm gets stiff and brittle over time and will cause the carburetor not to function.

I'd start by removing, dis-assembling and inspecting the carburetor.  Most likely it will need a carb rebuild kit, Tecumseh part number 631893.

Your engine may have points and a will have to verify the engine type or inspect to see if you engine has points.

Search You Tube for "Tecumseh diaphragm Toro S140 rebuild" and you will find several videos covering rebuilding the carburetor.


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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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