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QUESTION: Craftsman / Briggs Lawnmower Engine not starting

Tractor Model#:  Craftsman 917.275760
Engine Model #:  Briggs 31P777-0299-E1

Over time, the engine has become increasingly difficult to start.  Last night, it flat out refused.  I've tried a trickle charger, a full sized battery charger w/ 200-amp jump capability, I've changed the battery, checked the valve adjustment (.004 intake / .007 exhaust), even took the solenoid out of the loop by jumping straight from the + battery terminal straight to the starter motor, all with no luck.  

When I pull the spark plug, the engine rotates fairly freely, but seems to slow down as I let it spin.  I'd attribute this to the battery, but I just replaced it.  Once I put the plug back in, I maybe get 1/2-1 full rotation and then it just stops.  

I have yet to pull the starter and do anything with it because it's more work than anything else i've done, but it seems that's the last step in troubleshooting.

ANSWER: I have fixed many difficult starting issues by dis-connecting the battery calbes and cleaning the battery posts and battery cable ends with a wirebrush.  

Have you charged the battery and had it load tested to verify it is good.  I have had several new batteries that were defective.

I have not found very many defective starters but it does happen once in a while.  I find more bad battery cables and wires than bad starters.

Do you have voltmeter to check for voltage drop?


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

QUESTION: Battery terminals are clean and charged. Tractor is pretty old and it has been struggling to start for a while, which is why I suspect the starter. How would I go about trouble shooting?

There are two things I would test.  1) Current draw when tring to start the engine and 2) Voltage drop across the cables when tring to start.

Voltage is easier to check and the only tool you need is a voltmeter.  To check current you need a special shunt or special high current meter.

The link below describes how to check voltage drop.


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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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