The unit under test is a Troy-Bilt chipper made in the late 80's. Engine
is an 8 HP Briggs. It appears to have very low hours.
The engine starts easily, runs well for about 20 minutes, then begins to
drop RPM and return to normal operation. Loading appears to have no
effect. Eventually the engine will come to a halt. The engine will start
again, like a hit or miss engine, coughing puffs of smoke, and ramp up
to full operational speed.

So far:
Fresh gas with a healthy dose of Sea Foam.
Plug is new, dry, and a gray-cream color, no carbon.
New synthetic oil in the crankcase.

Any suggestions?

Kevin Gallimore

axolotl fired this volley in news:jt2df9$q09
:

Any suggestions?


If it's an updraft carb, they're easy to take apart and clean. It might
just be a sticking float valve. But it sounds like the magneto is giving
up after it gets hot.

I equipped an 8HP Briggs with an external coil for that reason, since the
12V charger portion of the maggy was still working.

LLoyd

axolotl fired this volley in news:jt2df9$q09$1
@dont-email.me:

Any suggestions?


Should have said, too... put in a new capacitor, and check the points gap
before you do anything else. Caps can fail hot, and the points may be worn
to where it's barely running right, anyway.

LLoyd

I'd want to check for bad ignition coil, or inadequate valve clearance.

Other things to check, try running with gas cap about 1/2 turn open, so it's
able to breathe in air.

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

"axolotl" wrote in message
...
The unit under test is a Troy-Bilt chipper made in the late 80's. Engine
is an 8 HP Briggs. It appears to have very low hours.
The engine starts easily, runs well for about 20 minutes, then begins to
drop RPM and return to normal operation. Loading appears to have no
effect. Eventually the engine will come to a halt. The engine will start
again, like a hit or miss engine, coughing puffs of smoke, and ramp up
to full operational speed.

So far:
Fresh gas with a healthy dose of Sea Foam.
Plug is new, dry, and a gray-cream color, no carbon.
New synthetic oil in the crankcase.

Any suggestions?

Kevin Gallimore

On 7/4/2012 5:48 PM, Lloyd E. Sponenburgh wrote:
axolotl fired this volley in news:jt2df9$q09
:

Any suggestions?


If it's an updraft carb, they're easy to take apart and clean. It might
just be a sticking float valve. But it sounds like the magneto is giving
up after it gets hot.

I equipped an 8HP Briggs with an external coil for that reason, since the
12V charger portion of the maggy was still working.

LLoyd


Thanks, Lloyd. Further research shows it has a "Magnetron" transistor
ignition. Heat and silicon being what they are, the module may be the
best place to look.

Kevin Gallimore

"Stormin Mormon" wrote in message
.. .
I'd want to check for bad ignition coil, or inadequate valve clearance.

Other things to check, try running with gas cap about 1/2 turn open, so
it's
able to breathe in air.


Bingo

Exhaust valve seat insert may be loose.

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
...
But it sounds like the magneto is giving
up after it gets hot.
...
LLoyd

Does it help to wash out an oil-soaked coil with solvent?

jsw

"Jim Wilkins" fired this volley in news:jt2lrn$9qn
:


Does it help to wash out an oil-soaked coil with solvent?

Not usually.

Oil, by itself, won't necessarily hurt a coil that's made properly,
unless it's one of the old tar-potted versions, and it has soaked for a
LONG time. Not likely to be tar, though, unless it's a pre-60's machine.

Solvents may harm it. If anything compromises the enamel on the magnet
wire they wound it from, it will kill the coil ASAP.

Besides, if the coil is potted - and most were since the 1940's - then
the oil didn't really get into the coil, just on it.

LLoyd

I've heard of that. and, also, exhaust valve seat may be burnt, and the
exhaust valve heats and lengthens.

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

"bw" wrote in message
...

"Stormin Mormon" wrote in message
.. .
I'd want to check for bad ignition coil, or inadequate valve clearance.

Other things to check, try running with gas cap about 1/2 turn open, so
it's
able to breathe in air.


Bingo

Exhaust valve seat insert may be loose.

I doubt it. Oil is non conductive, which is fine for this situation.

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

"Jim Wilkins" wrote in message
...

Does it help to wash out an oil-soaked coil with solvent?

jsw

Try using Premium gas that with octane in it. The older and newer
machines can't hack the Bio-gas they make now with alcohol in it -
as the former absorbs moisture out of the air and puts water in the gas.

The neighbor just go back his lawn tractor - new everything and tuned
up. He began to mow and after several hours put it up and went in for
night. He refilled the tank the next day (tank cooled and sucked in
water) and the engine acted like yours. Water in the lines, carb and
just in the gas.

Mine was like that - I parked it in the hot sun and while it was hot ran
it with some stp in the tank - the anti-Alcohol stuff - and it now runs.

Good Luck. And on small engines - never to much oil. It flood the engine.

Martin

On 7/4/2012 4:44 PM, axolotl wrote:
The unit under test is a Troy-Bilt chipper made in the late 80's. Engine
is an 8 HP Briggs. It appears to have very low hours.
The engine starts easily, runs well for about 20 minutes, then begins to
drop RPM and return to normal operation. Loading appears to have no
effect. Eventually the engine will come to a halt. The engine will start
again, like a hit or miss engine, coughing puffs of smoke, and ramp up
to full operational speed.

So far:
Fresh gas with a healthy dose of Sea Foam.
Plug is new, dry, and a gray-cream color, no carbon.
New synthetic oil in the crankcase.

Any suggestions?

Kevin Gallimore

axolotl wrote:

The unit under test is a Troy-Bilt chipper made in the late 80's. Engine
is an 8 HP Briggs. It appears to have very low hours.
The engine starts easily, runs well for about 20 minutes, then begins to
drop RPM and return to normal operation. Loading appears to have no
effect. Eventually the engine will come to a halt. The engine will start
again, like a hit or miss engine, coughing puffs of smoke, and ramp up
to full operational speed.

So far:
Fresh gas with a healthy dose of Sea Foam.
Plug is new, dry, and a gray-cream color, no carbon.
New synthetic oil in the crankcase.

Any suggestions?

Sounds like it is flooding. Since it takes 20 minutes to
show up, I would check the air filter, choke and fuel
mixture adjustment

-jim



Kevin Gallimore

Martin Eastburn fired this volley in
:

Try using Premium gas that with octane in it. The older and newer
machines can't hack the Bio-gas they make now with alcohol in it -
as the former absorbs moisture out of the air and puts water in the
gas.

Phooey. The only thing my 1962 Upright Briggs on my genset needed to be
alcohol compatible was re-adjusting the needle valve settings. At worst,
it might have needed a new needle valve, since it did have a cushioned
seat -- but it didn't.

Good Luck. And on small engines - never to much oil. It flood the
engine.

Martin, do you actually WANT them to destroy their engine? Over-filling
a recip is a bad way to end a good day. You don't "flood" the engine,
you fill it to the recommended fill height, and no higher.

LLoyd

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message

Phooey. The only thing my 1962 Upright Briggs on my genset needed
to be
alcohol compatible was re-adjusting the needle valve settings. At
worst,
it might have needed a new needle valve, since it did have a
cushioned
seat -- but it didn't.

LLoyd

I made an old flea-market Powermate 3.5KW generator run smoothly by
swapping the jet from 166 to a 162 that the repair shop thought might
work better.
The hole in the 166 is between 0.033" (#66 drill) and 0.036" (#64). I
don't have odd numbered sizes of tiny drills.
http://www.perr.com/phpBB3/viewtopic.php?f=14&t=5069

The 1950's 6BS engine on my lawnmower needed only a richer needle
setting.

jsw

Lloyd E. Sponenburgh wrote:
Martin Eastburn fired this volley in
:


Good Luck. And on small engines - never to much oil. It flood the
engine.

Martin, do you actually WANT them to destroy their engine?
Over-filling a recip is a bad way to end a good day. You don't
"flood" the engine, you fill it to the recommended fill height, and
no higher.

LLoyd

I understood him to mean don't put too much oil in them ... I sold a
really nice mower to a neighbor , idiot did just that . What started out as
a low-hours self propelled mower was in the junk pile before fall . I
shoulda kept that one and sold him the one I still have ...
--
Snag
Learning keeps
you young !

"Snag" fired this volley in
:

I understood him to mean don't put too much oil in them ... I sold a
really nice mower to a neighbor , idiot did just that . What started
out as a low-hours self propelled mower was in the junk pile before
fall . I shoulda kept that one and sold him the one I still have ...
--

Yeah, upon re-reading, I can see he might have meant that. It read sort
of like pidgeon English, and I thought he was meaning you could never
HAVE "to much oil".

In the re-interpreted case, I agree -- never add too much oil.

Lloyd

"the oil was low, so I put in a quart...."

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

"Snag" wrote in message
...

I understood him to mean don't put too much oil in them ... I sold a
really nice mower to a neighbor , idiot did just that . What started out as
a low-hours self propelled mower was in the junk pile before fall . I
shoulda kept that one and sold him the one I still have ...
--
Snag
Learning keeps
you young !

On Wed, 04 Jul 2012 16:48:12 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

axolotl fired this volley in news:jt2df9$q09
:

Any suggestions?


If it's an updraft carb, they're easy to take apart and clean. It might
just be a sticking float valve. But it sounds like the magneto is giving
up after it gets hot.

I equipped an 8HP Briggs with an external coil for that reason, since the
12V charger portion of the maggy was still working.

LLoyd

My old Case backhoe was acting the same way. After running it a while
it would start to miss and act like it was running rich. After cooling
for a day it would start and run fine then start running crappy after
about 20 minutes. After checking the points and plugs I put in a new
coil and the problem went away. It now starts easily just like before
and runs for hours without any problems.
Eric

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:

But it sounds like the magneto is giving
up after it gets hot.
If the run time is less when you restart it, then the magneto is
likely. I had a 5 Hp Briggs give this symptom, it would start from
cold and run fine for about 10 minutes, run rough and then quit.
If you waited a minute, it would restart, but only run a minute or
two before quitting. I pulled it up next to my car and put a timing
light on it, and it was clear the spark was dying when hot. The guy
at the mower shop tried to dissuade me from buying the part, wanted
me to bring it in for testing, but I just bought it and it fixed the
problem.

It was a plain coil and breaker ignition on that one.

Jon

On Jul 5, 2:49*pm, Jon Elson wrote:
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote:

*But it sounds like the magneto is giving up after it gets hot.

If the run time is less when you restart it, then the magneto is
likely. *I had a 5 Hp Briggs give this symptom, it would start from
cold and run fine for about 10 minutes, run rough and then quit.
If you waited a minute, it would restart, but only run a minute or
two before quitting. *I pulled it up next to my car and put a timing
light on it, and it was clear the spark was dying when hot. *The guy
at the mower shop tried to dissuade me from buying the part, wanted
me to bring it in for testing, but I just bought it and it fixed the
problem.

It was a plain coil and breaker ignition on that one.

Jon

Had a Snapper lawnmower I rescued from a dumpster with the same
problem. Got about 10 minutes of running, then it stopped and no
amount of messing would get it going again until it cooled off.
Replaced the magneto module and it's been running for 8 years. Was
$50, but a new mower of that type is over 1000. No points/capacitor,
it's an all-electronic sealed module. It works or it doesn't, all
there is for tweaking is the gap between the poles and the flywheel.
Tear off a flap of the shipping box and that's the gap gauge.

The other thing I've found is that the early '80s engines really want
premium gas, with the low end cheap stuff, it just stalls on tall
grass and weeds. Since this year is looking to be a 4-5 mow job one,
I can afford a gallon or two of 91 octane for the increase in
performance.

Stan