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Small Engines (Lawn Mowers, etc.)/mower engine cuts out under load


QUESTION: The mower: Montgomery Wards riding mower model# TMO-33551A A2540. The motor: Briggs and Stratton 18 hp. The problem:The engine starts up and then will idle fine forever at both low idle or high idle. But when I engage it in gear and the engine is under load, it dies within about 15 seconds. I have just acquired this mower and I changed the motor oil, the gear oil, checked the plugs(they look okay)and lubed the steering parts and levers. Is it likely that this is simply an air/fuel mixture problem? If so, do I need to remove the front of the mower to access the carburetor? Or is it likely to be some other issue? Thanks for any help.

ANSWER: Does the engine die when you engage the blades with the transaxle in neutral?

Is the engine an L-head opposed twin cylinder style?

It is possible the carburetor is dirty, on the high speed circuit as the throttle butterfly opens up when the engine is loaded and the high speed circuit delivers more fuel.

Do you have an air compressor?


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

QUESTION: The engine will run in gear for about 15-30 seconds, with or without the mower engaged. Idling in neutral, it just keeps running, no problems. As for the engine, it is a twin cylinder. L style? I'm not sure, the images I see on a google search are varied so I am not certain. And yes, I do have a compressor.

ANSWER: The first step I would take is to see if the issue is fuel or ignition.  

Does the mower start right back up after it stops if you put it back in neutral?


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

QUESTION: Yes, the mower will restart after cutting out, although the interesting thing is that restarting it seems to require me to close the choke, then open it fully as I am cranking the starter. So, a lot of the similar questions I have found on the web about this seem to be answered with "needs a valve adjustment".  Do you think that is a likely culprit?

I would start by rebuilding and cleaning the entire fuel system, new fuel filter and a carb kit.  This should rule out a fuel problem.

If it starts right back up then the ignition is probably fine.

Before doing anything else I would replace the spark plugs.  I recently spent way too much time on a Husky saw and it turned out to be a bad spark plug...$5 would have saved me several hours of time and troubleshooting as I could not find anything else wrong with the saw.

NEW spark plugs first!


Small Engines (Lawn Mowers, etc.)

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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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