MTD riding lawn mower blows smoke out of muffler and air filter. Briggs and Stratton engine.

I've got a 13 year old MTD riding lawn mower. It has a 12hp Briggs and Stratton engine. It ran fine one day and the next day it blew fire out of the muffler, (I didn't witness that with my own eyes) it has oil in the muffler and the last time I tried to start it, it spewed a lot of oil out of the air intake. Do you have any ideas as to what could cause this? I was suspecting the rings and I've taken the cylinder out. What am I looking for at this point? Upon visual inspection, I'm not seeing anything that catches my eye. Is a visual inspection enough to determine if the rings are bad? I was expecting to find something obvious since it went from working fine one day to broke the next. Maybe it's not the rings. Any other ideas or suggestions? Thanks for the help.
Dale
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On Thu, 12 Jul 2007 14:01:30 -0000, snipped-for-privacy@gmail.com wrote:

Who was running it when the problem occured? Did they hear a "Clunk"??

You removed the cylinder? Or just the head?

I'd look for a burned/mutant valve, among other things.

You should be able to tell if a ring is cracked, if the cylinder is off.

Look at everything that you can see. Are the valves warped? Is the cylinder scored/damaged? Is the block intact? Does the piston move properly and the valves open/close properly when you turn it over by hand?
Time to take a full inventory of functional motor components.
Puddin'
"Mit der Dummheit kaempfen Goetter selbst vergebens!" -Friedrich Schiller
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I removed the piston from the cylinder. None of the rings are cracked. The cylinder doesn't have any scores or doesn't appear to be warped. The valves open and close properly. When I manually pushed open the intake valve oil drained out of it. Could oil somehow be getting into this valve instead of leaking around the piston/rings? Can you think of anyway that's possible? I'll investigate that tonight. When I drained the oil, it was a nice mixture of oil and gas. Looking for more ideas. If I find anymore clues tonight, I'll post it. Thanks, Dale
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On Thu, 12 Jul 2007 16:32:06 -0000, snipped-for-privacy@gmail.com wrote:

Yes. A valve problem was my first guess.

Warped valve stem, maybe damage to the valve guide.

Ouch!, Ouch!, Ouch!, and Ouch! Are you sure?

I likely shouda mentioned I'm not familiar with your machine, just know a little about 4-stroke motors.
Is your B&S motor a "flathead" or is it OHV?
P
"Mit der Dummheit kaempfen Goetter selbst vergebens!" -Friedrich Schiller
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On Thu, 12 Jul 2007 16:32:06 -0000, snipped-for-privacy@gmail.com wrote:

(A compression check first .. before a piston is pulled)
This would be an excellent time to hone the cylinder and put new rings in.

Valves can "appear" to work properly. A weak spring can affect the working of the valve, so it may not completely seal.

Oren
..through the use of electrical or duct tape, achieve the configuration in the photo..
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On Jul 12, 9:01 am, snipped-for-privacy@gmail.com wrote:

Did you check the oil level before you tore it down? Overfilling the oil will cause it to blow out the muffler.
Red
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I've seen smaller B&S (maybe 5hp) with the horozontal cyl. smoking like crazy when overfilled with oil.
Dunno if the OP's 12hp is horozontal or vertical.
Never saw one blow fire out the muffler.
P
"Mit der Dummheit kaempfen Goetter selbst vergebens!" -Friedrich Schiller
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On Thu, 12 Jul 2007 23:42:05 GMT, Puddin' Man

Maybe after dark. The OP never saw it; but he pulled a piston?!
-- Oren
..through the use of electrical or duct tape, achieve the configuration in the photo..
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On Thu, 12 Jul 2007 17:43:23 -0700, Oren wrote:

I've seen oily mufflers spit fire. Seems a bit hasty for the OP to yank the engine apart looking for worn rings especially when it ran fine the previous time.
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Yes, it was definitely hasty (stupid) of me to yank the thing apart. I'm a beginner at small engines and I had three guys standing around confidently saying it's the rings. I acted impulsively and I'm now slapping myself for it. Live and learn I suppose. Anyways, I think you're right, it's going to end up being overfilled oil. I put the thing back together and I'm getting ready to fire it up and see what happens. Thanks for the advice so far.
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I fired it up and so far so good. Geesh!! Stick around. Next week I'll be doing a complete carb tear down when I run out of gas. LOL
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On Fri, 13 Jul 2007 11:49:41 -0000, snipped-for-privacy@gmail.com wrote:

Glad you can laugh at yourself :-)) -- Oren
..through the use of electrical or duct tape, achieve the configuration in the photo..
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On Fri, 13 Jul 2007 11:49:41 -0000, snipped-for-privacy@gmail.com wrote:

No offence, but, before you are awarded your PhD in small engine mechanics, I'd recommend "Problem Determination and Communication: 101". :-)
P
"Mit der Dummheit kaempfen Goetter selbst vergebens!" -Friedrich Schiller
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On Fri, 13 Jul 2007 03:06:53 -0000, snipped-for-privacy@gmail.com wrote:

And not a single one suggested a compression check.... -- Oren
..through the use of electrical or duct tape, achieve the configuration in the photo..
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My 18hp B&S twin cyl. has done it several times.
Red
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