The unit under test is a generator powered by an 8HP Briggs. I cleaned
the fuel tank, replaced the fuel lines and filter, and installed a
carburetor rebuild kit.

Engine starts and runs well for five or ten minutes, then stumbles and
stops. Starts up again with a single pull.

What should I be looking for?

Kevin Gallimore

Clogged vent, in the fuel cap. Try running with
the cap unscrewed, a half turn or so. If it runs
with the cap loose, look inside the cap for one
or more tiny holes. Clear the holes with a straight
pin.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"axolotl" wrote in message
...
The unit under test is a generator powered by an 8HP
Briggs. I cleaned the fuel tank, replaced the fuel lines
and filter, and installed a carburetor rebuild kit.

Engine starts and runs well for five or ten minutes, then
stumbles and stops. Starts up again with a single pull.

What should I be looking for?

Kevin Gallimore

On Sat, 24 Nov 2012 09:41:58 -0500, axolotl
wrote:

The unit under test is a generator powered by an 8HP Briggs. I cleaned
the fuel tank, replaced the fuel lines and filter, and installed a
carburetor rebuild kit.

Engine starts and runs well for five or ten minutes, then stumbles and
stops. Starts up again with a single pull.

What should I be looking for?

Kevin Gallimore

Fuel restriction somewhere? Could be plugged fuel cap vent or a
filter.

Pete Keillor

axolotl wrote:

The unit under test is a generator powered by an 8HP Briggs. I cleaned
the fuel tank, replaced the fuel lines and filter, and installed a
carburetor rebuild kit.

Engine starts and runs well for five or ten minutes, then stumbles and
stops. Starts up again with a single pull.

What should I be looking for?

Kevin Gallimore


There is a torrent of BS manuals out there, if anyone is interested.
I ran across the link when I was looking for a part to fix my mower a
while back. I didn't bother to copy the link.

Be prepared to choke the thing the next time it stops. If choking it or
squirting ether at it keeps it running , it's a fuel problem. If not, it's
either ignition or a valve temporarily hanging up.

I like the plugged gap cap idea.

Do the symptoms change under load?

Pete Stanaitis
---------------

"axolotl" wrote in message
...
The unit under test is a generator powered by an 8HP Briggs. I cleaned the
fuel tank, replaced the fuel lines and filter, and installed a carburetor
rebuild kit.

Engine starts and runs well for five or ten minutes, then stumbles and
stops. Starts up again with a single pull.

What should I be looking for?

Kevin Gallimore

On Sat, 24 Nov 2012 09:41:58 -0500, axolotl
wrote:

The unit under test is a generator powered by an 8HP Briggs. I cleaned
the fuel tank, replaced the fuel lines and filter, and installed a
carburetor rebuild kit.

Engine starts and runs well for five or ten minutes, then stumbles and
stops. Starts up again with a single pull.

What should I be looking for?

Loosen the gas cap and see if it still poops out. I'm thinking clogged
port in the gas cap. A stuck float would cause it to die quicker.

--
Good ideas alter the power balance in relationships, that is why
good ideas are always initially resisted. Good ideas come with a
heavy burden. Which is why so few people have them. So few people
can handle it.
-- Hugh Macleod

"axolotl" wrote in message
...
The unit under test is a generator powered by an 8HP Briggs. I cleaned the
fuel tank, replaced the fuel lines and filter, and installed a carburetor
rebuild kit.

Engine starts and runs well for five or ten minutes, then stumbles and
stops. Starts up again with a single pull.

What should I be looking for?

Kevin Gallimore

Stuck or misadjusted float.

PrecisionmachinisT wrote:


"axolotl" wrote in message
...
The unit under test is a generator powered by an 8HP Briggs. I cleaned
the fuel tank, replaced the fuel lines and filter, and installed a
carburetor rebuild kit.

Engine starts and runs well for five or ten minutes, then stumbles and
stops. Starts up again with a single pull.

What should I be looking for?

Kevin Gallimore

Stuck or misadjusted float.
I don't believe these recent engines use floats. They have a bowl above
the fuel tank that has fuel pumped by a vaccum-operated diaphragm,
and the excess fuel spills over back into the tank.

My guess is the magneto has gone bad, and fails when hot. If
you restart immediately, how long does it run the 2nd time?
If it gets progressively worse, each restart runs shorter than
the last one, that is a good indication it may be the magneto.
If you let it sit for 5-10 minutes before restarting, then it
runs much longer?

I had this exact problem on a 5 Hp recent Briggs engine.
I put a magnetic-coupled timing light on it, and saw the spark
got weak while running, and then no spark (no timing light
flashes) when it died. A new magneto coil fixed it.

Jon

On Sat, 24 Nov 2012 20:57:02 -0800, "PrecisionmachinisT"
wrote:


"axolotl" wrote in message
...
The unit under test is a generator powered by an 8HP Briggs. I cleaned the
fuel tank, replaced the fuel lines and filter, and installed a carburetor
rebuild kit.

Engine starts and runs well for five or ten minutes, then stumbles and
stops. Starts up again with a single pull.

What should I be looking for?

Kevin Gallimore

Stuck or misadjusted float.

Blocked filter ir fuel fitting at tank? Pull the hose off and do a
fuel flow test.

"Jon Elson" wrote in message
...
PrecisionmachinisT wrote:


"axolotl" wrote in message
...
The unit under test is a generator powered by an 8HP Briggs. I cleaned
the fuel tank, replaced the fuel lines and filter, and installed a
carburetor rebuild kit.

Engine starts and runs well for five or ten minutes, then stumbles and
stops. Starts up again with a single pull.

What should I be looking for?

Kevin Gallimore

Stuck or misadjusted float.
I don't believe these recent engines use floats. They have a bowl above
the fuel tank that has fuel pumped by a vaccum-operated diaphragm,
and the excess fuel spills over back into the tank.

My guess is the magneto has gone bad, and fails when hot. If
you restart immediately, how long does it run the 2nd time?
If it gets progressively worse, each restart runs shorter than
the last one, that is a good indication it may be the magneto.
If you let it sit for 5-10 minutes before restarting, then it
runs much longer?

I had this exact problem on a 5 Hp recent Briggs engine.
I put a magnetic-coupled timing light on it, and saw the spark
got weak while running, and then no spark (no timing light
flashes) when it died. A new magneto coil fixed it.



Depends on how old it is then I guess...I have a coleman generator and also
a lawnmower with B&S engines having float type carbs, indeed, both are
getting on in years.

The mower had a magneto went out on it a couple years ago...but in my case,
some days it simply would not put out any spark....

On 11/25/2012 7:46 PM, wrote:
On Sat, 24 Nov 2012 20:57:02 -0800, "PrecisionmachinisT"
wrote:


"axolotl" wrote in message
...
The unit under test is a generator powered by an 8HP Briggs. I cleaned the
fuel tank, replaced the fuel lines and filter, and installed a carburetor
rebuild kit.

Engine starts and runs well for five or ten minutes, then stumbles and
stops. Starts up again with a single pull.

What should I be looking for?

Kevin Gallimore

Stuck or misadjusted float.

Blocked filter ir fuel fitting at tank? Pull the hose off and do a
fuel flow test.


Today's fooling around yields slightly different symptoms. Starts, runs
with surging, about a 10 second rep rate.

Tank cap is not clogged, loosened the cap to make sure. Fuel filter
shows fuel on both sides of the filter media.

The engine wants the choke on, indicating too lean a mixture.

The governor slams back and forth as the engine is surging, indicating
that it is moving freely.

It is certainly possible that I screwed up the carb cleaning and rebuild.

What would be a good diagnostic test for the magneto? I replaced one in
a different Briggs not long ago, but that engine simply would not go
when hot.

Thanks,

Kevin Gallimore

axolotl wrote:

On 11/25/2012 7:46 PM, wrote:
On Sat, 24 Nov 2012 20:57:02 -0800, "PrecisionmachinisT"
wrote:


"axolotl" wrote in message
...
The unit under test is a generator powered by an 8HP Briggs. I cleaned the
fuel tank, replaced the fuel lines and filter, and installed a carburetor
rebuild kit.

Engine starts and runs well for five or ten minutes, then stumbles and
stops. Starts up again with a single pull.

What should I be looking for?

Kevin Gallimore

Stuck or misadjusted float.

Blocked filter ir fuel fitting at tank? Pull the hose off and do a
fuel flow test.


Today's fooling around yields slightly different symptoms. Starts, runs
with surging, about a 10 second rep rate.

Tank cap is not clogged, loosened the cap to make sure. Fuel filter
shows fuel on both sides of the filter media.

The fuel hose may have an internal restriction. It is
obviously getting some gas, but not enough.


The engine wants the choke on, indicating too lean a mixture.

Does the carb have mixture screw that you can adjust?




The governor slams back and forth as the engine is surging, indicating
that it is moving freely.

It is certainly possible that I screwed up the carb cleaning and rebuild.

What would be a good diagnostic test for the magneto? I replaced one in
a different Briggs not long ago, but that engine simply would not go
when hot.

Sounds more likely that something is clogged in the fuel system.
Either the fuel line, float valve or main jet may have some dirt
restricting flow. Or it might be running lean because the
intake is leaking air (bad gasket, loose bolts or cracked manifold).

You might also want to check that flywheel is timed
correctly.

On Sun, 25 Nov 2012 20:27:10 -0500, axolotl
wrote:

On 11/25/2012 7:46 PM, wrote:
On Sat, 24 Nov 2012 20:57:02 -0800, "PrecisionmachinisT"
wrote:


"axolotl" wrote in message
...
The unit under test is a generator powered by an 8HP Briggs. I cleaned the
fuel tank, replaced the fuel lines and filter, and installed a carburetor
rebuild kit.

Engine starts and runs well for five or ten minutes, then stumbles and
stops. Starts up again with a single pull.

What should I be looking for?

Kevin Gallimore

Stuck or misadjusted float.

Blocked filter ir fuel fitting at tank? Pull the hose off and do a
fuel flow test.


Today's fooling around yields slightly different symptoms. Starts, runs
with surging, about a 10 second rep rate.

Tank cap is not clogged, loosened the cap to make sure. Fuel filter
shows fuel on both sides of the filter media.

The engine wants the choke on, indicating too lean a mixture.

The governor slams back and forth as the engine is surging, indicating
that it is moving freely.

It is certainly possible that I screwed up the carb cleaning and rebuild.

What would be a good diagnostic test for the magneto? I replaced one in
a different Briggs not long ago, but that engine simply would not go
when hot.

Check for gasket air leaks, one of the most common problems.
Don't overtorque the carb when putting it on, either. DAMHIKT.

--
Good ideas alter the power balance in relationships, that is why
good ideas are always initially resisted. Good ideas come with a
heavy burden. Which is why so few people have them. So few people
can handle it.
-- Hugh Macleod

PrecisionmachinisT wrote:



Depends on how old it is then I guess...I have a coleman generator and
also a lawnmower with B&S engines having float type carbs, indeed, both
are getting on in years.

I've got 3 things with Briggs engines, I think they call them "Quantum"
series. They have the flat, pleated paper air filter under a swing-out
plastic cover. So, I think this has been the standard engine from
Briggs for about 20 years back, in the 5 and 8-HP size.

This carburetor design does seem to be pretty robust, the rest of the
engine is awfully flimsy. The main crank bearing is on a cover that
is so flimsy you can bend it with one hand. So, the thing that keeps
the two main bearings aligned is the crank itself! If the crank is
hit with a severe side load, like on a mower or wood chipper, there is no
block support for the crank, and it breaks in the middle. You can
guess how I know about that.

Jon

I've seen engines, where the gasket between the carb and the engine leaks
air. Usually, this means won't start, needs ether or gas poured into the air
intake to start. Not starts on one pull.

Sometimes, water in the gasoline will make engine stall, but restarts on one
pull. I'd want to pour out the gasoline into a glass jar, and see if water
settles out.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"axolotl"
wrote in message ...


The engine wants the choke on, indicating too lean a mixture.

Thanks,

Kevin Gallimore

I think magneto problems are typically that -- won't run when hot.

You're right, that's puzzling. I'm not getting any good answers.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"axolotl" wrote in message
...


Today's fooling around yields slightly different symptoms. Starts, runs
with surging, about a 10 second rep rate.

Tank cap is not clogged, loosened the cap to make sure. Fuel filter
shows fuel on both sides of the filter media.

The engine wants the choke on, indicating too lean a mixture.

The governor slams back and forth as the engine is surging, indicating
that it is moving freely.

It is certainly possible that I screwed up the carb cleaning and rebuild.

What would be a good diagnostic test for the magneto? I replaced one in
a different Briggs not long ago, but that engine simply would not go
when hot.

Thanks,

Kevin Gallimore

Some small engines run better, with a coating of Permatex IIb non hardening
gasket sealer, on the carb to engine gasket. Messy stuff to work with, but
comes off with alcohol.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"Larry Jaques" wrote in message
...

Check for gasket air leaks, one of the most common problems.
Don't overtorque the carb when putting it on, either. DAMHIKT.

On Sun, 25 Nov 2012 20:27:10 -0500, axolotl
wrote:

On 11/25/2012 7:46 PM, wrote:
On Sat, 24 Nov 2012 20:57:02 -0800, "PrecisionmachinisT"
wrote:


"axolotl" wrote in message
...
The unit under test is a generator powered by an 8HP Briggs. I cleaned the
fuel tank, replaced the fuel lines and filter, and installed a carburetor
rebuild kit.

Engine starts and runs well for five or ten minutes, then stumbles and
stops. Starts up again with a single pull.

What should I be looking for?

Kevin Gallimore

Stuck or misadjusted float.

Blocked filter ir fuel fitting at tank? Pull the hose off and do a
fuel flow test.


Today's fooling around yields slightly different symptoms. Starts, runs
with surging, about a 10 second rep rate.

Tank cap is not clogged, loosened the cap to make sure. Fuel filter
shows fuel on both sides of the filter media.

The engine wants the choke on, indicating too lean a mixture.

The governor slams back and forth as the engine is surging, indicating
that it is moving freely.

It is certainly possible that I screwed up the carb cleaning and rebuild.

What would be a good diagnostic test for the magneto? I replaced one in
a different Briggs not long ago, but that engine simply would not go
when hot.

Thanks,

Kevin Gallimore
Feed propane or acetylene into the intake and see if it runs well. If
so, it's not the mag.

I had a mower with a Honda engine with all the same symptoms.
Cleaning the spark plug and carburetor etc. did no good.

The internet had the answer.
Change the spark plug. That worked. It must have
been shorting out when it warmed up. That might happen on Briggs too.

On Saturday, November 24, 2012 9:41:51 AM UTC-5, axolotl wrote:
The unit under test is a generator powered by an 8HP Briggs. I cleaned

the fuel tank, replaced the fuel lines and filter, and installed a

carburetor rebuild kit.



Engine starts and runs well for five or ten minutes, then stumbles and

stops. Starts up again with a single pull.



What should I be looking for?



Kevin Gallimore

Stormin Mormon wrote:


What would be a good diagnostic test for the magneto? I replaced one in
a different Briggs not long ago, but that engine simply would not go
when hot.
If you have an inductive timing light, that is a great tool. When the
spark is weak, the light will not fire regularly. When the spark basically
goes away, the light will not fire at all. if the light flickers and then
quits just about the same time the engine quits, that is a really strong
indication of weak spark. It the timing light continues to blink
right down to the engine's last stroke, the problem is probably NOT
ignition.

Jon

I have a LawnBoy that drove us nuts. It was way too lean,
requiring choke to stay running.

We did everything, including replacing the top & bottom seals
on the crank. That helped some, but it's never been really
fixed. It has begun running better of late, but we don't know
why.... [mechanic's shrug]


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433