The patient is a 1000W Yamaha EF1000is inverter generator. The 50cc
four cycle engine drives an alternator that powers an inverter which
outputs clean 120V 60Hz power.

In normal "economy" mode the speed of the engine is controlled so the
alternator's ouput is adequate to maintain output power. With the
economy mode off the engine runs at constant speed, about 5000 RPM.

The engine starts easily and idles smoothly. A little puff of black
smoke when started, exhaust seems clean immediately after that.

By applying load slowly with a variac the generator ramps up and runs
fine 'til about 50% load, after which it dies.

A relatively small load will kill the engine if it's applied quickly,
regardless of whether economy mode is on or not. The manual recommends
turning economy mode off for loads with starting surges, e.g., motors.

What's been done:
Cleaned and gapped the plug which looked a little dark, but not too
bad. I haven't replaced it yet.

The spark arrestor was well carboned; cleaning helped some.

The carb bowl had a little sediment, but I've seen worse. I cleaned
it, the jet, and venturi tube with no apparent effect. The owner's
manual does not give any info on carb adjustments.

Fuel pump seems to be working, at least at pull cranking speed.

Air cleaner element looks fine; no significant difference running
without it.

Not done:
Replace plug, adjust valves, compression check.

Currently I'm thinking that the lack of full power and the inability
to pull even a relatively small load up quickly are the relevant
symptoms.

I don't think there's a problem with the inverter controls. The
control may be shutting the engine down when it can't keep up with
demand, rather than allowing it a chance to catch up, which is how
it's intended to operate. The inverter wants to supply either good
power, or none at all.

My short term goal is to try to decide whether it's worth spending $50
on a service manual, or to just use the thing. The intended use is to
run a couple lights and perhaps a laptop or TV for short power
outages, so it'd probably do that as-is.

--
Ned Simmons

On Sun, 08 Mar 2009 13:49:50 -0800, Winston
wrote:

Ned Simmons wrote:
The patient is a 1000W Yamaha EF1000is inverter generator. The 50cc
four cycle engine drives an alternator that powers an inverter which
outputs clean 120V 60Hz power.

(...)

Your variac is gonna be really reactive, power factor wise.
The inverter may be getting confused about the phase shift
between the voltage its supplying and the current demand
that follows.

It's not my department, but won't the PF of a transformer driving a
resisitive load be close to unity, once the xformer's start-up surge
has passed? My load is a space heater of wattage close to the
generator's rating.


Have you tried it on a purely resistive load like increasing
numbers of incandescent lights?

No, I thought of that, but haven't been ambitious enough yet to gather
all the lamps in the house that still have tungsten lamps in one
place. g The "relatively small" load I spoke of that kills the
generator is a large 310W soldering iron (not a gun). I understand the
iron will draw more current cold than hot, but haven't checked how
much more.

I'm pretty confident the motor is not performing up to spec, but
you're probably right in that I don't have a real good fix on just how
off it is.

--
Ned Simmons

Ned Simmons wrote:
The patient is a 1000W Yamaha EF1000is inverter generator. The 50cc
four cycle engine drives an alternator that powers an inverter which
outputs clean 120V 60Hz power.

(...)

Your variac is gonna be really reactive, power factor wise.
The inverter may be getting confused about the phase shift
between the voltage its supplying and the current demand
that follows.

Have you tried it on a purely resistive load like increasing
numbers of incandescent lights?

--Winston


--

Don't *faff*, dear.

Ned Simmons writes:


By applying load slowly with a variac the generator ramps up and runs
fine 'til about 50% load, after which it dies.

Can you see the throttle control? By that I mean whatever opens the
throttle in response to load. It's an solonoid, I suspect....

Is it slamming shut, or opening further to no avail?


--
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

It's the carb, doood. High speed jet clogged. Hose it out again.
JR
Dweller in the cellar

On Sun, 08 Mar 2009 15:16:42 -0500, Ned Simmons
wrote:

The patient is a 1000W Yamaha EF1000is inverter generator. The 50cc
four cycle engine drives an alternator that powers an inverter which
outputs clean 120V 60Hz power.

In normal "economy" mode the speed of the engine is controlled so the
alternator's ouput is adequate to maintain output power. With the
economy mode off the engine runs at constant speed, about 5000 RPM.

The engine starts easily and idles smoothly. A little puff of black
smoke when started, exhaust seems clean immediately after that.

By applying load slowly with a variac the generator ramps up and runs
fine 'til about 50% load, after which it dies.

A relatively small load will kill the engine if it's applied quickly,
regardless of whether economy mode is on or not. The manual recommends
turning economy mode off for loads with starting surges, e.g., motors.

What's been done:
Cleaned and gapped the plug which looked a little dark, but not too
bad. I haven't replaced it yet.

The spark arrestor was well carboned; cleaning helped some.

The carb bowl had a little sediment, but I've seen worse. I cleaned
it, the jet, and venturi tube with no apparent effect. The owner's
manual does not give any info on carb adjustments.

Fuel pump seems to be working, at least at pull cranking speed.

Air cleaner element looks fine; no significant difference running
without it.

Not done:
Replace plug, adjust valves, compression check.

Currently I'm thinking that the lack of full power and the inability
to pull even a relatively small load up quickly are the relevant
symptoms.

I don't think there's a problem with the inverter controls. The
control may be shutting the engine down when it can't keep up with
demand, rather than allowing it a chance to catch up, which is how
it's intended to operate. The inverter wants to supply either good
power, or none at all.

My short term goal is to try to decide whether it's worth spending $50
on a service manual, or to just use the thing. The intended use is to
run a couple lights and perhaps a laptop or TV for short power
outages, so it'd probably do that as-is.

Ned Simmons wrote:
On Sun, 08 Mar 2009 13:49:50 -0800, Winston
wrote:

Ned Simmons wrote:
The patient is a 1000W Yamaha EF1000is inverter generator. The 50cc
four cycle engine drives an alternator that powers an inverter which
outputs clean 120V 60Hz power.
(...)

Your variac is gonna be really reactive, power factor wise.
The inverter may be getting confused about the phase shift
between the voltage its supplying and the current demand
that follows.

It's not my department, but won't the PF of a transformer driving a
resisitive load be close to unity, once the xformer's start-up surge
has passed?

No. The current peak through a purely inductively reactive load
will continue to arrive 90° later than the voltage peak as long
as the load is connected.

My load is a space heater of wattage close to the
generator's rating.

As you say below, incandescent loads draw much more current
when cold than when they are hot. Your clamp-on ammeter
will tell you if the relatively cold space heater is
causing the inverter to current - limit.

You might have the 'Perfect Storm' test there!
(Reactive load at maximum current).

Have you tried it on a purely resistive load like increasing
numbers of incandescent lights?

No, I thought of that, but haven't been ambitious enough yet to gather
all the lamps in the house that still have tungsten lamps in one
place. g The "relatively small" load I spoke of that kills the
generator is a large 310W soldering iron (not a gun). I understand the
iron will draw more current cold than hot, but haven't checked how
much more.

If you can get a Hall effect current probe and plug it into
your digital storage scope, you could get a good idea of how
much power that soldering iron draws in the first few cycles.
You would find that interesting and a little depressing.

I'm pretty confident the motor is not performing up to spec, but
you're probably right in that I don't have a real good fix on just how
off it is.

I'm beginning to understand why generator demonstrations often
include a load panel of dozens of incandescent lamps. The inrush
of each additional lamp is not all that high and power factor ~1.0.

It can be impressive but it's almost like cheating.

--Winston

--

Don't *faff*, dear.

On Sun, 08 Mar 2009 15:01:21 -0800, JR North
wrote:

It's the carb, doood. High speed jet clogged. Hose it out again.

That's encouraging. It does act as though it could be starving for
fuel. The high speed jet is what's called the "main jet" (#22) in this
page from the parts manual, right?
http://www.suscom-maine.net/~nsimmon...YamahaCarb.jpg

I looked at it and #19 under magnification before blowing them out and
they looked clear, but the orifice in that jet is mighty small. If
that's the right jet, I'll try it again.

--
Ned Simmons

On Sun, 8 Mar 2009 22:43:58 +0000 (UTC), David Lesher
wrote:

Ned Simmons writes:


By applying load slowly with a variac the generator ramps up and runs
fine 'til about 50% load, after which it dies.

Can you see the throttle control? By that I mean whatever opens the
throttle in response to load. It's an solonoid, I suspect....

It's a tiny stepper motor.


Is it slamming shut, or opening further to no avail?

It's hard to see working alone the way I had things set up, but I'm
pretty sure the throttle is opening and the engine fails to respond.
To be 100% sure I'll have to get someone to apply the load while I
watch the throttle. The symptoms would be consistent with the throttle
actuator responding too slowly to increasing load.

--
Ned Simmons

On Mar 8, 4:16*pm, Ned Simmons wrote:
The patient is a 1000W Yamaha EF1000is inverter generator. The 50cc
four cycle engine drives an alternator that powers an inverter which
outputs clean 120V 60Hz power.

In normal "economy" mode the speed of the engine is controlled so the
alternator's ouput is adequate to maintain output power. With the
economy mode off the engine runs at constant speed, about 5000 RPM.

The engine starts easily and idles smoothly. A little puff of black
smoke when started, exhaust seems clean immediately after that.

By applying load slowly with a variac the generator ramps up and runs
fine 'til about 50% load, after which it dies.

A relatively small load will kill the engine if it's applied quickly,
regardless of whether economy mode is on or not. The manual recommends
turning economy mode off for loads with starting surges, e.g., motors.

What's been done:
Cleaned and gapped the plug which looked a little dark, but not too
bad. I haven't replaced it yet.

The spark arrestor was well carboned; cleaning helped some.

The carb bowl had a little sediment, but I've seen worse. I cleaned
it, the jet, and venturi tube with no apparent effect. The owner's
manual does not give any info on carb adjustments.

Fuel pump seems to be working, at least at pull cranking speed.

Air cleaner element looks fine; no significant difference running
without it.

Not done:
Replace plug, adjust valves, compression check.

Currently I'm thinking that the lack of full power and the inability
to pull even a relatively small load up quickly are the relevant
symptoms.

I don't think there's a problem with the inverter controls. The
control may be shutting the engine down when it can't keep up with
demand, rather than allowing it a chance to catch up, which is how
it's intended to operate. The inverter wants to supply either good
power, or none at all.

My short term goal is to try to decide whether it's worth spending $50
on a service manual, or to just use the thing. The intended use is to
run a couple lights and perhaps a laptop or TV for short power
outages, so it'd probably do that as-is.

--
Ned Simmons

Sounds like it may be to lean to accept the load. As others have
noted, see what the throttle is doing when it won't accept the load.
It's probably opening up to no avail. If the jets are clean and you
have good fuel flow, make sure the float level is correct if this is a
float type carb., otherwise check for any air leaks that might be
leaning it out. It does not take much of an air leak on an engine
this small to give a lean condition. As these carbs don't usually
have an accelerator pump, the carb needs to be a tiny bit net rich to
accept a load increase when the governer pops the throttle open. Weak
ignition can also behave somewhat like a lean condition, as a lean
mixture takes more voltage to fire as does increased cylinder pressure
which occurs when the load is increased. Make sure you have a healthy
spark, ie it can jump at least 3/8".

Ned Simmons wrote:

The patient is a 1000W Yamaha EF1000is inverter generator. The 50cc
four cycle engine drives an alternator that powers an inverter which
outputs clean 120V 60Hz power.


Are your jets adjustable?

Wes

Winston writes:

Ned Simmons wrote:
On Sun, 08 Mar 2009 13:49:50 -0800, Winston
wrote:

Ned Simmons wrote:
The patient is a 1000W Yamaha EF1000is inverter generator. The 50cc
four cycle engine drives an alternator that powers an inverter which
outputs clean 120V 60Hz power.
(...)

Your variac is gonna be really reactive, power factor wise.
The inverter may be getting confused about the phase shift
between the voltage its supplying and the current demand
that follows.

It's not my department, but won't the PF of a transformer driving a
resisitive load be close to unity, once the xformer's start-up surge
has passed?

No. The current peak through a purely inductively reactive load
will continue to arrive 90° later than the voltage peak as long
as the load is connected.


It's been a long time since EE 412, Transformers and Machines. But
surely the transformer input should reflect the output, +/- 3dB [as the
joke goes...]

Otherwise, EVERY load on the grid would appear to be fully reactive to
the grid; as there's not a consumer out that who isn't fed via multiple
transformers. [132KV-13.2KV; then 13.2 to 240/120, etc]

I'd sooner blame the high speed jet...


--
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

Winston wrote:

If you can get a Hall effect current probe and plug it into
your digital storage scope, you could get a good idea of how
much power that soldering iron draws in the first few cycles.
You would find that interesting and a little depressing.

If I didn't miss something, this is a resistive soldering iron. Ohming it and doing the
calcs would give worst case load.

Wes

"Ned Simmons" wrote in message
...
The patient is a 1000W Yamaha EF1000is inverter generator. The 50cc
four cycle engine drives an alternator that powers an inverter which
outputs clean 120V 60Hz power.

In normal "economy" mode the speed of the engine is controlled so the
alternator's ouput is adequate to maintain output power. With the
economy mode off the engine runs at constant speed, about 5000 RPM.

The engine starts easily and idles smoothly. A little puff of black
smoke when started, exhaust seems clean immediately after that.

By applying load slowly with a variac the generator ramps up and runs
fine 'til about 50% load, after which it dies.

A relatively small load will kill the engine if it's applied quickly,
regardless of whether economy mode is on or not. The manual recommends
turning economy mode off for loads with starting surges, e.g., motors.

What's been done:
Cleaned and gapped the plug which looked a little dark, but not too
bad. I haven't replaced it yet.

The spark arrestor was well carboned; cleaning helped some.

The carb bowl had a little sediment, but I've seen worse. I cleaned
it, the jet, and venturi tube with no apparent effect. The owner's
manual does not give any info on carb adjustments.

Fuel pump seems to be working, at least at pull cranking speed.

Air cleaner element looks fine; no significant difference running
without it.

Not done:
Replace plug, adjust valves, compression check.

Currently I'm thinking that the lack of full power and the inability
to pull even a relatively small load up quickly are the relevant
symptoms.

I don't think there's a problem with the inverter controls. The
control may be shutting the engine down when it can't keep up with
demand, rather than allowing it a chance to catch up, which is how
it's intended to operate. The inverter wants to supply either good
power, or none at all.

My short term goal is to try to decide whether it's worth spending $50
on a service manual, or to just use the thing. The intended use is to
run a couple lights and perhaps a laptop or TV for short power
outages, so it'd probably do that as-is.

--
Ned Simmons

With the obvious safety precautions, try emptying the gas tank, cleaning
or replacing the filter/strainer and using fresh gasoline. It could be
the fuel is flowing insufficiently from the tank and starving the pump
and the floatbowl under high loads.

On Sun, 8 Mar 2009 16:50:52 -0700 (PDT), oldjag
wrote:


Sounds like it may be to lean to accept the load. As others have
noted, see what the throttle is doing when it won't accept the load.
It's probably opening up to no avail. If the jets are clean and you
have good fuel flow, make sure the float level is correct if this is a
float type carb., otherwise check for any air leaks that might be
leaning it out. It does not take much of an air leak on an engine
this small to give a lean condition. As these carbs don't usually
have an accelerator pump, the carb needs to be a tiny bit net rich to
accept a load increase when the governer pops the throttle open. Weak
ignition can also behave somewhat like a lean condition, as a lean
mixture takes more voltage to fire as does increased cylinder pressure
which occurs when the load is increased. Make sure you have a healthy
spark, ie it can jump at least 3/8".

It also needs to be a tiny bit net rich to make sure that the piston
crown remains in one piece. Air cooled engines and lean running, not
a good combination.

Change the plug - it's a cheap problem point to eliminate.

Might need to run a video camera watching the throttle as you load
it up - Paint the linkage for good contrast. It could open fully as
suspected, but once the computer sees that the engine isn't responding
to the throtle call and working harder after a second or two, it slams
to Off and does a load dump. You would need to review the video to
see it.

Rig your own variable load bank - get a Contractors Work Light
string with ten lamps, and then you can screw in the lamps one at a
time (with gloves on!) to vary the load.

-- Bruce --

Ned Simmons used his keyboard to write :
The patient is a 1000W Yamaha EF1000is inverter generator. The 50cc
four cycle engine drives an alternator that powers an inverter which
outputs clean 120V 60Hz power.

In normal "economy" mode the speed of the engine is controlled so the
alternator's ouput is adequate to maintain output power. With the
economy mode off the engine runs at constant speed, about 5000 RPM.

The engine starts easily and idles smoothly. A little puff of black
smoke when started, exhaust seems clean immediately after that.

By applying load slowly with a variac the generator ramps up and runs
fine 'til about 50% load, after which it dies.

A relatively small load will kill the engine if it's applied quickly,
regardless of whether economy mode is on or not. The manual recommends
turning economy mode off for loads with starting surges, e.g., motors.

What's been done:
Cleaned and gapped the plug which looked a little dark, but not too
bad. I haven't replaced it yet.

The spark arrestor was well carboned; cleaning helped some.

The carb bowl had a little sediment, but I've seen worse. I cleaned
it, the jet, and venturi tube with no apparent effect. The owner's
manual does not give any info on carb adjustments.

Fuel pump seems to be working, at least at pull cranking speed.

Air cleaner element looks fine; no significant difference running
without it.

Not done:
Replace plug, adjust valves, compression check.

Currently I'm thinking that the lack of full power and the inability
to pull even a relatively small load up quickly are the relevant
symptoms.

I don't think there's a problem with the inverter controls. The
control may be shutting the engine down when it can't keep up with
demand, rather than allowing it a chance to catch up, which is how
it's intended to operate. The inverter wants to supply either good
power, or none at all.

If it is similiar to the Honda inverter models, on an overload
condition the inverter stops outputting, but the engine keeps running.
An engine restart is required for the output to resume.


My short term goal is to try to decide whether it's worth spending $50
on a service manual, or to just use the thing. The intended use is to
run a couple lights and perhaps a laptop or TV for short power
outages, so it'd probably do that as-is.

On Sun, 08 Mar 2009 19:28:56 -0600, "Pete C."
wrote:



Dismantle the carb, run in an ultrasonic cleaner with a good solvent,
blow all the ports clear and dry with compressed air, reassemble.

Since the consensus is that the problem is in the carb, I'll do that
once I've had a closer look at how the throttle actuator is behaving.

--
Ned Simmons

On Sun, 08 Mar 2009 19:56:05 -0400, Wes wrote:

Ned Simmons wrote:

The patient is a 1000W Yamaha EF1000is inverter generator. The 50cc
four cycle engine drives an alternator that powers an inverter which
outputs clean 120V 60Hz power.


Are your jets adjustable?

Not the main jet. There is a limited adjustment on what I assume is
the idle mixture.

--
Ned Simmons

On Sun, 8 Mar 2009 18:00:39 -0700, "Mal Boswick"
wrote:

With the obvious safety precautions, try emptying the gas tank, cleaning
or replacing the filter/strainer and using fresh gasoline. It could be
the fuel is flowing insufficiently from the tank and starving the pump
and the floatbowl under high loads.


There's a strainer in the tank neck; as far as I can tell there's no
filter in the tank or between the tank and carb. The pump seems to
push plenty of fuel -- it only took a few pulls to refill the carb
after draining the bowl. I did wonder if there's any problem that
would cause the pump, which is apparently powered by crankcase
pressure, to lose flow at higher engine speeds.

--
Ned Simmons

On Sun, 08 Mar 2009 20:43:41 -0800, Winston
wrote:

David Lesher wrote:
(...)

Otherwise, EVERY load on the grid would appear to be fully reactive to
the grid; as there's not a consumer out that who isn't fed via multiple
transformers. [132KV-13.2KV; then 13.2 to 240/120, etc]

I'd sooner blame the high speed jet...

I bow to your experience here.
Still, I think that space heater is going to draw more current
in its relatively cold state than when it warms up.

Absolutely. I calculated power by measuring both current and voltage
at the heater.

--
Ned Simmons

On Sun, 8 Mar 2009 16:50:52 -0700 (PDT), oldjag
wrote:



Sounds like it may be to lean to accept the load. As others have
noted, see what the throttle is doing when it won't accept the load.
It's probably opening up to no avail. If the jets are clean and you
have good fuel flow, make sure the float level is correct if this is a
float type carb., otherwise check for any air leaks that might be
leaning it out. It does not take much of an air leak on an engine
this small to give a lean condition.

A leak wouldn't surprise me. The carb mounts outside a plastic shroud
that surrounds the engine, and as best as I can tell, the shoud is
sandwiched between the carb and engine. When I removed the carb, the
gasket between the carb and shroud looked OK, but I have no idea
what's going on at the other interface.

As these carbs don't usually
have an accelerator pump, the carb needs to be a tiny bit net rich to
accept a load increase when the governer pops the throttle open.

Right, no accelerator pump.

Weak
ignition can also behave somewhat like a lean condition, as a lean
mixture takes more voltage to fire as does increased cylinder pressure
which occurs when the load is increased. Make sure you have a healthy
spark, ie it can jump at least 3/8".

Probably wise to replace the plug as well then, but that means a trip
to town.

--
Ned Simmons

On Sun, 8 Mar 2009 21:15:01 -0500, "Don Young"
wrote:

I learned that regardless of cleaning or appearance, a new spark plug will
sometimes clear up mysterious engine troubles, including failure to
accelerate or develop adequate power. Your symptoms are classic for fuel
starvation, but even things like stale fuel, weak ignition, or restricted
exhaust can have very similar symptoms.

Then a fresh plug is on the list for the next time I go to town. I did
get a noticeable improvement after cleaning the carbon out of the
spark arrester.

--
Ned Simmons

On Sun, 08 Mar 2009 21:30:54 -0500, Wayne
wrote:


I don't think there's a problem with the inverter controls. The
control may be shutting the engine down when it can't keep up with
demand, rather than allowing it a chance to catch up, which is how
it's intended to operate. The inverter wants to supply either good
power, or none at all.

If it is similiar to the Honda inverter models, on an overload
condition the inverter stops outputting, but the engine keeps running.
An engine restart is required for the output to resume.

You're right, it should behave as you describe when overloaded.

--
Ned Simmons

Wes wrote:
Winston wrote:

If you can get a Hall effect current probe and plug it into
your digital storage scope, you could get a good idea of how
much power that soldering iron draws in the first few cycles.
You would find that interesting and a little depressing.

If I didn't miss something, this is a resistive soldering iron. Ohming it and doing the
calcs would give worst case load.

Well if you need a *simple* answer, OK.



--Winston

--

Don't *faff*, dear.

David Lesher wrote:
(...)

Otherwise, EVERY load on the grid would appear to be fully reactive to
the grid; as there's not a consumer out that who isn't fed via multiple
transformers. [132KV-13.2KV; then 13.2 to 240/120, etc]

I'd sooner blame the high speed jet...

I bow to your experience here.
Still, I think that space heater is going to draw more current
in its relatively cold state than when it warms up.

We seldom can power a 1KW load with a 1KW generator, simply
because most loads have additional power requirements for
inrush.

--Winston


--

Don't *faff*, dear.

"Ned Simmons" wrote in message
...
On Sun, 08 Mar 2009 21:30:54 -0500, Wayne
wrote:


I don't think there's a problem with the inverter controls. The
control may be shutting the engine down when it can't keep up with
demand, rather than allowing it a chance to catch up, which is how
it's intended to operate. The inverter wants to supply either good
power, or none at all.

If it is similiar to the Honda inverter models, on an overload
condition the inverter stops outputting, but the engine keeps running.
An engine restart is required for the output to resume.

You're right, it should behave as you describe when overloaded.

--
Ned Simmons



The next thing to check is the high voltage coil that is breaking down.
Magneto coils have a habit of doing that. I had one that was doing exactly
the same thing as yours. dropping out under heavy load. After doing all the
usual stuff with the carb. I finally put an ohm meter on the coil secondary
and it was open but still ran the engine under a light to medium load. It
was a 7 kw generator but would only load up to about 3 kw. and then conk
out.


John

On Mar 8, 3:16*pm, Ned Simmons wrote:
The patient is a 1000W Yamaha EF1000is inverter generator. The 50cc
four cycle engine drives an alternator that powers an inverter which
outputs clean 120V 60Hz power.

In normal "economy" mode the speed of the engine is controlled so the
alternator's ouput is adequate to maintain output power. With the
economy mode off the engine runs at constant speed, about 5000 RPM.

The engine starts easily and idles smoothly. A little puff of black
smoke when started, exhaust seems clean immediately after that.

By applying load slowly with a variac the generator ramps up and runs
fine 'til about 50% load, after which it dies.

A relatively small load will kill the engine if it's applied quickly,
regardless of whether economy mode is on or not. The manual recommends
turning economy mode off for loads with starting surges, e.g., motors.

What's been done:
Cleaned and gapped the plug which looked a little dark, but not too
bad. I haven't replaced it yet.

The spark arrestor was well carboned; cleaning helped some.

The carb bowl had a little sediment, but I've seen worse. I cleaned
it, the jet, and venturi tube with no apparent effect. The owner's
manual does not give any info on carb adjustments.

Fuel pump seems to be working, at least at pull cranking speed.

Air cleaner element looks fine; no significant difference running
without it.

Not done:
Replace plug, adjust valves, compression check.

Currently I'm thinking that the lack of full power and the inability
to pull even a relatively small load up quickly are the relevant
symptoms.

I don't think there's a problem with the inverter controls. The
control may be shutting the engine down when it can't keep up with
demand, rather than allowing it a chance to catch up, which is how
it's intended to operate. The inverter wants to supply either good
power, or none at all.

My short term goal is to try to decide whether it's worth spending $50
on a service manual, or to just use the thing. The intended use is to
run a couple lights and perhaps a laptop or TV for short power
outages, so it'd probably do that as-is.

--
Ned Simmons

If you don’t have the owner’s manual, I found it he
http://www.yamaha-motor.com/assets/s...01-19_1109.pdf
There’s a wiring diagram on pg. 33.

Ned Simmons writes:


A leak wouldn't surprise me. The carb mounts outside a plastic shroud
that surrounds the engine, and as best as I can tell, the shoud is
sandwiched between the carb and engine. When I removed the carb, the
gasket between the carb and shroud looked OK, but I have no idea
what's going on at the other interface.


Propane torch is the way to find such leaks. Twenty years ago,
cars were CHOKED with hoses going every which way.

[I watched a friend work on totally screwed up one. I asked "How's it
going?" and he said "THIS one was connected to the carb.." The other end
of that hose was ... the washer reservoir..."]

When you HEAR a loose hose but can't figure out which... or suspect
a carb gasket leak... just squirt some propane around. When the engine
sits up and idles smoothly, you're there.

Thankfully Detroit finally discovered digital computers...



--
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

Winston writes:

David Lesher wrote:
(...)

Otherwise, EVERY load on the grid would appear to be fully reactive to
the grid; as there's not a consumer out that who isn't fed via multiple
transformers. [132KV-13.2KV; then 13.2 to 240/120, etc]

I'd sooner blame the high speed jet...

I bow to your experience here. Still, I think that space heater is
going to draw more current in its relatively cold state than when it
warms up.


With lamps, quite true. Not so with heaters that are cooler than that....

We seldom can power a 1KW load with a 1KW generator, simply because most
loads have additional power requirements for inrush.

That is quite true...


--
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

On Mar 9, 12:06*am, Ned Simmons wrote:
..
Then a fresh plug is on the list for the next time I go to town. I did
get a noticeable improvement after cleaning the carbon out of the
spark arrester.
Ned Simmons

The smell of the exhaust is different for rich, normal and lean
mixtures. Put your fingers in front of the exhaust for a second and
then sniff them.You might be able to calibrate your nose to the
differences by playing with the idle mix screw on another engine
running the same gas.

On Mon, 9 Mar 2009 06:07:28 +0000 (UTC), the infamous David Lesher
scrawled the following:

Ned Simmons writes:


A leak wouldn't surprise me. The carb mounts outside a plastic shroud
that surrounds the engine, and as best as I can tell, the shoud is
sandwiched between the carb and engine. When I removed the carb, the
gasket between the carb and shroud looked OK, but I have no idea
what's going on at the other interface.


Propane torch is the way to find such leaks. Twenty years ago,
cars were CHOKED with hoses going every which way.

[I watched a friend work on totally screwed up one. I asked "How's it
going?" and he said "THIS one was connected to the carb.." The other end
of that hose was ... the washer reservoir..."]

When you HEAR a loose hose but can't figure out which... or suspect
a carb gasket leak... just squirt some propane around. When the engine
sits up and idles smoothly, you're there.

It always amazes me when someone suggests using flammable liquids or
gases to locate a leak on an engine. One guy I read about used
gasoline in a squirt bottle until he was killed from the fire which
started as the gas dripped onto the exhaust system. Others explode
with ether in their hands. What fun!

I suggest (to Ned and all) the use of -water- as a leak finder. Any
flammable liquid or gas will go into the intake and cause an RPM jump
(said the guy who used to use Berryman's B12 in his young and foolish
days.) Water being sucked into the intake leak makes a loud slurping
noise while the engine slows and is a much safer and better test
liquid.

--
The wealth required by nature is limited and is easy to procure;
but the wealth required by vain ideals extends to infinity.
--Epicurus, Principal Doctrines

Larry Jaques writes:

When you HEAR a loose hose but can't figure out which... or suspect
a carb gasket leak... just squirt some propane around. When the engine
sits up and idles smoothly, you're there.

It always amazes me when someone suggests using flammable liquids or
gases to locate a leak on an engine. One guy I read about used
gasoline in a squirt bottle until he was killed from the fire which
started as the gas dripped onto the exhaust system. Others explode
with ether in their hands. What fun!


I would never squirt gasoline like that. A propane torch puts out a small
amount of gas, and propane is not ether; plus an open hood with the fan
going is hardly a closed chamber.

I'd skip squirting water around a warm engine as it's a good way to crack
something. One exception is a mist sprayed into the carb throat; you can
actually clean carbon out with that..


--
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

On Mon, 9 Mar 2009 01:39:51 -0400, "John"
wrote:



The next thing to check is the high voltage coil that is breaking down.
Magneto coils have a habit of doing that. I had one that was doing exactly
the same thing as yours. dropping out under heavy load. After doing all the
usual stuff with the carb. I finally put an ohm meter on the coil secondary
and it was open but still ran the engine under a light to medium load. It
was a 7 kw generator but would only load up to about 3 kw. and then conk
out.


John

Thanks to all who responded. I was happy that there were no
suggestions to replace the jug, piston and rings (not gonna happen).

The agenda, starting with the easiest:
-replace plug
-check spark and coil
-observe throttle actuator as load increases to make sure its behavior
seems appropriate
-drain fuel tank (into my '54 Farmall which ain't fussy) and refill
with fresh fuel
-check for air leaks
-tear carb down and clean thoroughly
-reluctantly spend $50 on a shop manual (RTFM)

I'll report on the outcome, but I may not get back to it 'til next
weekend.

--
Ned Simmons

Ned Simmons wrote:
The patient is a 1000W Yamaha EF1000is inverter generator. The 50cc
four cycle engine drives an alternator that powers an inverter which
outputs clean 120V 60Hz power.

In normal "economy" mode the speed of the engine is controlled so the
alternator's ouput is adequate to maintain output power. With the
economy mode off the engine runs at constant speed, about 5000 RPM.

The engine starts easily and idles smoothly. A little puff of black
smoke when started, exhaust seems clean immediately after that.

By applying load slowly with a variac the generator ramps up and runs
fine 'til about 50% load, after which it dies.

A bad spark plug could be the cause, or perhaps a
bad magneto coil. Will it run indefinitely at 50%
load? If it runs a while, then sputters and dies
at 50%, that is a strong sign of a bad magneto.
Another possible cause is a plugged-up jet in the
carb. Up to 50% the idle/low-speed circuit gives
an ignitable mixture, above that, the high-speed
jet is needed, and isn't working. If you run it
at 50% for an extended period, with a really lean
mixture, it will fry the engine.

Jon