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

On Thu, 12 Jul 2007 14:01:30 -0000, wrote:

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)

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

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.

You removed the cylinder? Or just the head?

What am I
looking for at this point?

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

Upon visual inspection, I'm not seeing
anything that catches my eye. Is a visual inspection enough to
determine if the rings are bad?

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

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?

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

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

On Thu, 12 Jul 2007 16:32:06 -0000, wrote:

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?

Yes. A valve problem was my first guess.

Can you think
of anyway that's possible?

Warped valve stem, maybe damage to the valve guide.

I'll investigate that tonight.
When I drained the oil, it was a nice mixture of oil and gas.

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

Looking for more ideas. If I find anymore clues tonight, I'll post
it.

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

On Jul 12, 9:01 am, wrote:
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

Did you check the oil level before you tore it down? Overfilling the
oil will cause it to blow out the muffler.

Red

On Thu, 12 Jul 2007 16:32:06 -0000, wrote:

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.

(A compression check first .. before a piston is pulled)

This would be an excellent time to hone the cylinder and put new rings
in.

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.

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

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
--
Oren

...through the use of electrical or duct tape, achieve the configuration in the photo..

On Thu, 12 Jul 2007 13:17:50 -0700, Red wrote:

On Jul 12, 9:01 am, wrote:
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

Did you check the oil level before you tore it down? Overfilling the
oil will cause it to blow out the muffler.

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

On Thu, 12 Jul 2007 23:42:05 GMT, Puddin' Man
wrote:

Never saw one blow fire out the muffler.

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..

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.

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

On Fri, 13 Jul 2007 11:49:41 -0000, wrote:

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

Glad you can laugh at yourself :-))
--
Oren

...through the use of electrical or duct tape, achieve the configuration in the photo..

On Fri, 13 Jul 2007 03:06:53 -0000, wrote:

I'm a beginner at small engines and I had three guys standing around
confidently saying it's the rings.

And not a single one suggested a compression check....
--
Oren

...through the use of electrical or duct tape, achieve the configuration in the photo..

On Fri, 13 Jul 2007 11:49:41 -0000, wrote:

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

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

On Jul 12, 6:42 pm, Puddin' Man wrote:


Did you check the oil level before you tore it down? Overfilling the
oil will cause it to blow out the muffler.

I've seen smaller B&S (maybe 5hp) with the horozontal cyl. smoking
like crazy when overfilled with oil.


My 18hp B&S twin cyl. has done it several times.

Red