btw...when I got it running off the jump start from my car, I shut it off. It was running fine and didn't just die.

I have had the same problem with a Sears Craftsman lawn tractor with a Briggs and Stratton engine. For me, the problem turned out to be the valves. (I am not very handy, so this may not be your problem). Since it probably has overhead valves, you can check them by taking off the hood and unscrewing 4 bolts. Look for a pushrod poking through the rocker arm. You can also buy a feeler gauge and check that the valves are in spec. Again, I am not very handy, but I experienced the exact same symptoms twice, and it was the valves both times. (Pushrod pushed through the rocker arm the first time, pushrod ripped apart the cylinder head the second time).

Speaking of which (and not to hijack your thread, but . . .) does anyone know why the intake valve pushrod would be pushing so hard as to do this? I have been pushing the tractor pretty hard lately, hauling dirt and bags of cement. Could that cause this (both times happened within 6 months). Either way, as soon as my new cylinder head comes, I am gonna replace it and pray it doesn't happen again, unless someone has a better idea.

The adjuster nut probably works loose and the adjustment vibrates letting the nut turn and making the adjustment off.

I have pages on adjusting the valves for your engine copied from the B&S Service Manual IF you would like them. Address below, put in proper format.

Walt Conner
wconner5 at verizon dot net

Fuzzylogic2me...did you do the valve replacement the first time it happened? I would consider myself moderately handy but haven't done anything like a valve replacement.

walt...it couldn't hurt. Do you have an electronic copy? Let me know and I'll e-mail you.

Thanks for the replies.

Wait...would it have started and stayed running if there were an issue with the valves? I can't imagine that it would've.

I mean the one time it worked with a jump start it sounded completely fine and ran until I turned it off with the key. That seems like an important clue to me...that it started and ran (once) when juiced by the car battery. But now the jump won't do it...

"would it have started and stayed running if there were an issue with the valves? I can't imagine that it would've."
Yes, it would continue stay running, if you can get it to crank well enough to start up. The problem with the valves on Briggs that affects the cranking (only) is that when the valves wear, that makes the compression release function poorly, so poorly in fact, you are lucky if you can get it to spin at all. Perform a valve adjustment, and do it correctly, you will be amazed at the difference.

So I took off the starter, opened it up, it looked fine, put it back together, and it bench tested it...where it spun up fine. I greased the gear-pinion assembly up good, put it back on the tractor, and she started right up.

My guess is the the gear-pinion assembly was just sticking. I should've tried bench testing the starter before I took it apart though...just so I'd know if it was the gear-pinion sticking or if the starter was just bound (or something along those lines). I'm guessing it was the gear-pinion...

Thanks for the suggestions...I'm sure I could still use a valve adjustment.

"When I turn the key (with the clutch and seat safety switches engaged), the starter will spin the flywheel/gear-ring a revolution or two and then everything stops."

"I greased the gear-pinion assembly up good, put it back on the tractor, and she started right up."

Your fix does not fit your symptoms you describe. Starter gear should not be "greased up"

Walt Conner

Agree with Walt's assessment. My guess is that you "accidently" improved the electrical circuit contact connections, allowing more power to the starter motor.

I'm having the same problem with my Sears Craftsman 27HP B&S.
Model 446977 Type 0472. Replaced battery, starter. It's getting juice to the starter/engaging the gear. It turns the flywheel about 1/2 turn and stops. You can still hear humming (solenoid?). I can hand-turn the flywheel to release the starter gear, repeat, but with same result. Removed both plugs, and it would then turn-over..Replace plugs though, and the same result..1/2 turn and then nothing. Sounds like compression/valve type problem, which sounds no good..:(

You probably threw good money after the starter and battery for nothing. You need to adjust the valves so the compression release will work properly during cranking the engine. Your symptoms are a classic case.

You found this thread; now read the earlier postings, especially from Walt Conner about adjusting the valves. Send him an email and he'll bounce back with an instruction sheet.

Except that Walt's e-mail is now
wconner5 at frontier dot com

Thanks guys..Just tried Walt's 3rd email address. Hope it works !! The original battery needed replacing (can't believe it lasted 7 yrs.).. the starter was probably good, but only got $40 sunk it it. We'll see.. Aggravating problem, to say the least.