Can anyone help? I have a Mountfiled Empress 4hp petrol mower that I
obtained from someone who inherited it and wasn't sure if it was working or
not. I got it home, put some unleaded petrol in the tank, checked the oil
level and cleaned the air filter. After only a few pulls of the pull-cord,
it fired up and the engine seems to run smoothly and steadily. However, it
does seem to lack power and after cutting some grass for a few feet, it
seemed to gradually lose power. This continued even with the blades lifted
off the grass, and no matter how I set the throttle.

Can anyone suggest a logical sequence of things I should check?

TIA for any help!

Al

"AL_n" wrote in
:

Can anyone help? I have a Mountfiled Empress 4hp petrol mower that I
obtained from someone who inherited it and wasn't sure if it was
working or not. I got it home, put some unleaded petrol in the tank,
checked the oil level and cleaned the air filter. After only a few
pulls of the pull-cord, it fired up and the engine seems to run
smoothly and steadily. However, it does seem to lack power and after
cutting some grass for a few feet, it seemed to gradually lose power.
This continued even with the blades lifted off the grass, and no
matter how I set the throttle.

Can anyone suggest a logical sequence of things I should check?

TIA for any help!

Al


PS... Now when I try to fire it up, it starts up OK, but then dies out
after about one second...

On 19/08/2012 13:56, AL_n wrote:
"AL_n" wrote in
:

Can anyone help? I have a Mountfiled Empress 4hp petrol mower that I
obtained from someone who inherited it and wasn't sure if it was
working or not. I got it home, put some unleaded petrol in the tank,
checked the oil level and cleaned the air filter. After only a few
pulls of the pull-cord, it fired up and the engine seems to run
smoothly and steadily. However, it does seem to lack power and after
cutting some grass for a few feet, it seemed to gradually lose power.
This continued even with the blades lifted off the grass, and no
matter how I set the throttle.

Can anyone suggest a logical sequence of things I should check?

TIA for any help!

Al


PS... Now when I try to fire it up, it starts up OK, but then dies out
after about one second...

Not enough petrol getting through. Is the vent hole in the filler cap clear?

David Hill wrote in
:

Not enough petrol getting through. Is the vent hole in the filler cap
clear?

David,
Thank you for the suggestion. There doesn't appear to be a vent hole in the
filler cap. However, I tried starting it with the cap unscrewed and it
still dies as soon as it fires up.

Al

On 19 Aug 2012 12:56:24 GMT, AL_n wrote:

Can anyone suggest a logical sequence of things I should check?

In was going to say check the fan/vane/throttle linkages and springs for
correctness and not bent gunked up etc. Note that these linkages quite
often have huge amounts of slack in them a springs that a also slack in
the rest state. Best to get a diagram of the layout rather than guess...

PS... Now when I try to fire it up, it starts up OK, but then dies out
after about one second...

But that sounds like fuel starvation. Is the breather hole in the tank
clear? Does it run with the cap loose? Is the fuel filter clear? Time to
dismantle inspect the tank/carb/gaskets. As it did run well before do not
be tempted to adjust any of the jets or poke anything through orfices.
Backwards washing with clean fuel or a gentle blast of compressed air
should clear any miniscule spots of gunk.

--
Cheers
Dave.

"Dave Liquorice" wrote in
ll.co.uk:

But that sounds like fuel starvation. Is the breather hole in the tank
clear? Does it run with the cap loose? Is the fuel filter clear? Time
to dismantle inspect the tank/carb/gaskets. As it did run well before
do not be tempted to adjust any of the jets or poke anything through
orfices. Backwards washing with clean fuel or a gentle blast of
compressed air should clear any miniscule spots of gunk.

Dave,
Thanks... There is no breather hole in the fuel cap. Even with the cap
loose, it still dies out immediately after it fires up. I'm OK with
dismantling things if necessary, but where is the fuel filter located? Is
it easy to access?

Al

On 19 Aug 2012 13:40:44 GMT, AL_n wrote:

Thanks... There is no breather hole in the fuel cap.

There will be but it might not be obvious but as it still dies with the
cap off that isn't overly relevant.

Even with the cap I'm OK with dismantling things if necessary, but
where is the fuel filter located? Is it easy to access?

What make engine is it, beinga "Mountfield" brand I suspect it will be a
Briggs & Stratton. If so wander over to the B&S web site and get the full
manual for your engine, might take a bit of digging and finding the
actual model number of your engine, there are guides on the site where to
find that on the various engines.

The fuel filter, my smaller B&S engine, is a fine delicate mesh cylinder
that dips into the fuel tank from the carb. IIRC remove the carb/tank
assembly from the engine (two bolts) then split the carb from the tank be
careful of the reienforced rubber gasket between the carb and tank as
that forms the fuel pump and has a couple of flap valves built into it.

Might be worth checking the plug and spark before attacking the
carb/tank.

--
Cheers
Dave.

"AL_n" wrote:

. Even with the cap
loose, it still dies out immediately after it fires up.

If it dies out immediately, there's something blocking the carb...is this a
conventional bowl-type carb? If so, it ought to run for a few minutes just
on that fuel....if the tank and fuel line are OK (pull the line off the
carb and see if fuel runs out), a carb cleaning and/or overhaul is called
for. Often depending on the supplier, and new carb is cheaper.

Disclaimer:
I'm on the other side of the pond, and don't know Mountfield at all, but
I've dealt with a lot of small engines on various garden implements of
death and destruction.

--
Gary Woods AKA K2AHC- PGP key on request, or at home.earthlink.net/~garygarlic
Zone 5/4 in upstate New York, 1420' elevation. NY WO G

"Dave Liquorice" wrote
But that sounds like fuel starvation. Is the breather hole in the tank
clear? Does it run with the cap loose? Is the fuel filter clear? Time to
dismantle inspect the tank/carb/gaskets. As it did run well before do not
be tempted to adjust any of the jets or poke anything through orfices.
Backwards washing with clean fuel or a gentle blast of compressed air
should clear any miniscule spots of gunk.

I'll second that, usually it's quite simple to cure. Either there is a bleed
tap on the bottom of the carb to let any accumulated muck out (is that just
Honda?) or you need to take the carb off the engine, take it apart and clean
it out (usually two or three screws). Old stale petrol in the tank is
probably the cause although it may be rust from inside the tank mucking
things up.
Make sure you do this in the open and away from any possible ignition
source.
--
Regards. Bob Hobden.
Posted to this Newsgroup from the W of London, UK

"Dave Liquorice" wrote in
ll.co.uk:


beinga "Mountfield" brand I suspect it will be
a Briggs & Stratton. If so wander over to the B&S web site and get the
full manual for your engine, might take a bit of digging and finding
the actual model number of your engine

Dave,
Thanks a million - that is the key info I needed. Yes, it does appear to be
a B&S engine; I have now found the printable manual at the B&S site and I'm
printing it out right now...

Al

"Bob Hobden" wrote in
:

"Dave Liquorice" wrote
But that sounds like fuel starvation. Is the breather hole in the tank
clear? Does it run with the cap loose? Is the fuel filter clear? Time
to dismantle inspect the tank/carb/gaskets. As it did run well before
do not be tempted to adjust any of the jets or poke anything through
orfices. Backwards washing with clean fuel or a gentle blast of
compressed air should clear any miniscule spots of gunk.

I'll second that, usually it's quite simple to cure. Either there is a
bleed tap on the bottom of the carb to let any accumulated muck out
(is that just Honda?) or you need to take the carb off the engine,
take it apart and clean it out (usually two or three screws). Old
stale petrol in the tank is probably the cause although it may be rust
from inside the tank mucking things up.
Make sure you do this in the open and away from any possible ignition
source.

Does the carb have a float?
If it does then you can often have a leak there. The float will sink and
oversaturate the petrol/air mixture.
An engine can often be started then die out after this flood of petrol.

Baz

Martin wrote in
news
On Sun, 19 Aug 2012 16:25:17 GMT, Baz wrote:

"Bob Hobden" wrote in
:

"Dave Liquorice" wrote
But that sounds like fuel starvation. Is the breather hole in the tank
clear? Does it run with the cap loose? Is the fuel filter clear? Time
to dismantle inspect the tank/carb/gaskets. As it did run well before
do not be tempted to adjust any of the jets or poke anything through
orfices. Backwards washing with clean fuel or a gentle blast of
compressed air should clear any miniscule spots of gunk.

I'll second that, usually it's quite simple to cure. Either there is a
bleed tap on the bottom of the carb to let any accumulated muck out
(is that just Honda?) or you need to take the carb off the engine,
take it apart and clean it out (usually two or three screws). Old
stale petrol in the tank is probably the cause although it may be rust
from inside the tank mucking things up.
Make sure you do this in the open and away from any possible ignition
source.

Does the carb have a float?
If it does then you can often have a leak there. The float will sink and
oversaturate the petrol/air mixture.
An engine can often be started then die out after this flood of petrol.

Do we know if the plug is wet or dry after the engine stops? Is there
a spark on the plug after the engine stops?

I had a problem on an outboard like this. It was caused by the
capacitor. I also had one on a motorbike caused by a cracked sparking
plug.

Well that could be the Points. Advanced ignition timing and a weak mixture
can cause overheating. Smash the porcelain on the plug.

Baz

Gary Woods wrote in
:

If it dies out immediately, there's something blocking the carb...is
this a conventional bowl-type carb? If so, it ought to run for a few
minutes just on that fuel....if the tank and fuel line are OK (pull
the line off the carb and see if fuel runs out), a carb cleaning
and/or overhaul is called for. Often depending on the supplier, and
new carb is cheaper.

Thanks... I followed your suggestion and pulled the fuel line off at the
tank, and fuel was flowing from the tank no problem. Next I unscrewd the
float chamber and it had fuel in it. The float chamber is screwed in place
by some kind of brass, threaded main-jet-like-thing. I blew through the
tiny hole therein, in case it was blocked. I checked that the throttle
cable was adjusted correctly. After that, it fired up first time and runs
with ample power now. I'm not sure what I did that cured it. Perhaps there
was a speck of debris in the main-jet-like-thing in the centre of the float
chamber.

Thanks to everyone for the help!

Al

"AL_n" wrote in
:

"Dave Liquorice" wrote in
ll.co.uk:


beinga "Mountfield" brand I suspect it will be
a Briggs & Stratton. If so wander over to the B&S web site and get
the full manual for your engine, might take a bit of digging and
finding the actual model number of your engine

Dave,
Thanks a million - that is the key info I needed. Yes, it does appear
to be a B&S engine; I have now found the printable manual at the B&S
site and I'm printing it out right now...


PS.... Unfortunately the manual doesn't go as far as describing how to
service the carb. However, I have cured the fault, somehow, after taking
the float chamber off and blowing out the jet in the centre of it.

Thanks again to all for the suggestions.

Al

Here are a couple of videos on repairing B & S carbs, whether they're the same as yours I no not.
CARBURETOR Repair on Older BRIGGS & STRATTON 3.5HP Engine Part 1 of 2 - YouTube
HOW TO REPAIR Lawnmower with BRIGGS & STRATTON Pulsa Prime Carburetor 1/2 - YouTube