I have an MTD, self propelled lawm mower with a 5.5 HP Briggs and
Stratton engine. Over the last several weeks, it has developed a
problem where it starts right up, runs for about 20 minutes and
stops. Sometimes it coughs and sputters for awhile before stalling,
other times it's as if it was turned off. There have been times it's
done that and would restart, other times, I have to wait until the
next day.
I have checked the air filter, checked the gas line, and checked the
spark plug cable. What I haven't done is replaced the spark plug.
If this helps, I thought it started moving alot faster about the time
it happened but for the life of me, I can't see how that would be
connected to the problem.

If it ran faster just before it died , it may be an indication that it is
being starved of fuel. Most small engines will rev. somewhat when they run
out of fuel. Is there a fuel filter to check? Is there dirt getting into the
needle valve? Is the float sticking closed? Is the carburetor dirty? Is
there water or dirt in the tank?
wrote in message
ups.com...
I have an MTD, self propelled lawm mower with a 5.5 HP Briggs and
Stratton engine. Over the last several weeks, it has developed a
problem where it starts right up, runs for about 20 minutes and
stops. Sometimes it coughs and sputters for awhile before stalling,
other times it's as if it was turned off. There have been times it's
done that and would restart, other times, I have to wait until the
next day.
I have checked the air filter, checked the gas line, and checked the
spark plug cable. What I haven't done is replaced the spark plug.
If this helps, I thought it started moving alot faster about the time
it happened but for the life of me, I can't see how that would be
connected to the problem.

rile,

As gas is drawn from the gas tank air must come in through a valve,
typically a cheap reed valve. These valves can fail. So you run the mower
until a vacuum builds up in the gas tank and stops the flow of gas. Next
time it stops take the gas cap off, put it back on, and try to start it. If
it starts up then suspect the reed valve.

Dave M.

the only thing using a reed valve is a two stroke, and that would have
nothing to do with building a vacuum in the tank.


s


"David Martel" wrote in message
ink.net...
rile,

As gas is drawn from the gas tank air must come in through a valve,
typically a cheap reed valve. These valves can fail. So you run the mower
until a vacuum builds up in the gas tank and stops the flow of gas. Next
time it stops take the gas cap off, put it back on, and try to start it.
If it starts up then suspect the reed valve.

Dave M.

On Aug 1, 1:59 pm, "Steve Barker"
wrote:
the only thing using a reed valve is a two stroke, and that would have
nothing to do with building a vacuum in the tank.

s

"David Martel" wrote in message

ink.net...



rile,

As gas is drawn from the gas tank air must come in through a valve,
typically a cheap reed valve. These valves can fail. So you run the mower
until a vacuum builds up in the gas tank and stops the flow of gas. Next
time it stops take the gas cap off, put it back on, and try to start it.
If it starts up then suspect the reed valve.

Dave M.- Hide quoted text -

- Show quoted text -

Well, strange as it may seem, I may agree with the gas cap theory. I
had thought of that before. Everytime I take the gas cap off, it
seems to run for awhile and then stall. It seems to me that as the
fuel level goes down, there has to be a means to prevent a vacuum from
disrupting the fuel flow. Could it be a bad gas cap? I'd run it
without one as a test but don't like the idea of gas splashing out of
the tank onto the hot engine.

The cap usually has a vent. It may be plugged.
wrote in message
oups.com...
On Aug 1, 1:59 pm, "Steve Barker"
wrote:
the only thing using a reed valve is a two stroke, and that would have
nothing to do with building a vacuum in the tank.

s

"David Martel" wrote in message

ink.net...



rile,

As gas is drawn from the gas tank air must come in through a valve,
typically a cheap reed valve. These valves can fail. So you run the
mower
until a vacuum builds up in the gas tank and stops the flow of gas.
Next
time it stops take the gas cap off, put it back on, and try to start
it.
If it starts up then suspect the reed valve.

Dave M.- Hide quoted text -

- Show quoted text -

Well, strange as it may seem, I may agree with the gas cap theory. I
had thought of that before. Everytime I take the gas cap off, it
seems to run for awhile and then stall. It seems to me that as the
fuel level goes down, there has to be a means to prevent a vacuum from
disrupting the fuel flow. Could it be a bad gas cap? I'd run it
without one as a test but don't like the idea of gas splashing out of
the tank onto the hot engine.

Rile,

You've already done the test by taking the cap off. You have a bad valve
or vent. Look at the cap, is it vented? Drain the tank, get a flashlight,
and look for a valve. This is a really cheap fix, you owe me a cup of
coffee.

Dave M.

5/5 HB Briggs don't have reed valves. Only found on two strokes.

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
..

"David Martel" wrote in message
ink.net...
: rile,
:
: As gas is drawn from the gas tank air must come in through a
valve,
: typically a cheap reed valve. These valves can fail. So you run
the mower
: until a vacuum builds up in the gas tank and stops the flow of
gas. Next
: time it stops take the gas cap off, put it back on, and try to
start it. If
: it starts up then suspect the reed valve.
:
: Dave M.
:
:

Run with the gas cap loosened about 1/4 turn, see if that helps.

My couple thoughts were
* Bad motor oil, as strange as that sounds.
* Valve clearance problem, if it's an older motor
* Ignition coil going bad

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
..

wrote in message
oups.com...
: Well, strange as it may seem, I may agree with the gas cap
theory. I
: had thought of that before. Everytime I take the gas cap off,
it
: seems to run for awhile and then stall. It seems to me that as
the
: fuel level goes down, there has to be a means to prevent a
vacuum from
: disrupting the fuel flow. Could it be a bad gas cap? I'd run
it
: without one as a test but don't like the idea of gas splashing
out of
: the tank onto the hot engine.
:

If the engine is more than a few years old, it may have valve
clearance problems. To check this isn't all that hard, with a
socket set and a couple of feeler gages.

To fix it requires dissembling the engine, and not many people
have the tools. I tried to make a living of small engine repairs,
and I do have the tools.

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
..

wrote in message
ups.com...
: I have an MTD, self propelled lawm mower with a 5.5 HP Briggs
and
: Stratton engine. Over the last several weeks, it has developed
a
: problem where it starts right up, runs for about 20 minutes and
: stops. Sometimes it coughs and sputters for awhile before
stalling,
: other times it's as if it was turned off. There have been
times it's
: done that and would restart, other times, I have to wait until
the
: next day.
: I have checked the air filter, checked the gas line, and
checked the
: spark plug cable. What I haven't done is replaced the spark
plug.
: If this helps, I thought it started moving alot faster about
the time
: it happened but for the life of me, I can't see how that would
be
: connected to the problem.
: