Smarty wrote:
....

... the bellows does not sit unloaded without
stress as it should, and I need to take a closer look at it. Maybe the
clamps they use are somehow deformed.

That ain't no clamp problem; the carb intake centerline is well below
that of the air filter. You need to do whatever it takes to line them
up -- ideal would be if there's play in the mounting holes for the
filter base that would let it be moved down sufficiently. Otherwise
either shim under the engine to raise it, elongate mounting holes for
the filter or combinations of both or whatever it takes.

It's clear that kind of stress on a light rubber piece will shorten life
significantly.

--

dpb wrote:

Smarty wrote:
...

... the bellows does not sit unloaded without
stress as it should, and I need to take a closer look at it. Maybe
the clamps they use are somehow deformed.

That ain't no clamp problem; the carb intake centerline is well below
that of the air filter. You need to do whatever it takes to line
them up -- ideal would be if there's play in the mounting holes for
the filter base that would let it be moved down sufficiently.
Otherwise either shim under the engine to raise it, elongate mounting
holes for the filter or combinations of both or whatever it takes.

It's clear that kind of stress on a light rubber piece will shorten
life significantly.

Since the weather was permitting today, I disassembled all of the
related parts and confirmed that there is a misalignment of the type
you described, maybe a total of 2 to 3 mm of vertical offset and
another mm or 2 of lateral offset. This definitely puts a pre-load on
the bellows, and I will have to concur that the stresses must be the
root cause of the weakening / wearing of the bellows prematurely.

I intend to correct the vertical offset by elongating the mounting
holes into vertical slots. I will probably get a little more wiggle
room horizontally as well, probably enough to gain a mm or so laterally.

I will report back on my progress.

Many thanks once again, and I have recognized the value of photography
to solve these types of problems.

On 7/23/2010 9:33 AM, Smarty wrote:
Smarty wrote:

The Daring Dufas wrote:

On 7/23/2010 12:14 AM, Smarty wrote:
Nate Nagel wrote:

On 07/22/2010 05:02 PM, Smarty wrote:
chaniarts wrote:

Smarty wrote:
I personally installed a Generac natural gas stand-by
generator 5 years ago, after a freak October ice storm
knocked out electricity in this area for nearly 2 weeks.

..snip..

I am open to any ideas and suggestions, and much
appreciate your time in reading this, and possibly
replying. Thank you very much.

home depot has 1.5" diameter silicone water tubing. if it's
not too high a temp, that may do you. it'll be far cheaper
to just buy a few feet of it and cut off lengths a few
times/year as pm.

I spent most of today searching out, buying, and trying the
'loop of hose' method, only to learn that the bending radius
for hose of this large dimension creates a loop which just
will not fit in the generator cabinet and also will not clear
the very limited adjacent carburettor linkages, governor
calibration screw, and assorted other parts. The stronger
radiator hose with internal helical wire is sturdy but very
difficult to bend to a tight loop. I did not buy a piece of
silicone tube, but I did play with some and it is also quite
stiff due to the thick walls, preventing a small radius bend.

I have ordered a couple hump connectors and lined T-bolt
clamps, and also have 3 more Generac bellows here which came
from my parts supplier. I am going to experiment further to
see what remaining options I have, including coating the
bellows, installing the hump hose, or possibly relocating
things slightly. I am quite certain that there is no way to
significantly move the air cleaner assembly without serious
re-design of the internal cabinet brackets, sheet-metal, and
plastic housing, none of which I have any real desire to screw
around with. Using the current placement of everything, I am
down to either a strengthened bellows, a hump hose, or
replacing the standard bellows every 9 months or so in the
preventative maintenance cycle.

The failure of the 2 bellows are fairly similar, small holes
not much bigger than a pin hole, developing on the moving
engine / carburettor side of the connection (versus the air
filter stationary side).

I would guess that the peak-to-peak vibration of the bellows
creates maybe a 3/8" to 1/2" excursion in the worn area of the
rubber at the engine rotation frequency (3600 RPM as I
recall). The damn bellows has a wall thickness of no more
than about 1/16th of an inch of rubber, and is far from being
a "heavy duty" construction compared to the hoses and hump
parts I see with 4mm thickness or more.

I will update as I learn more. Thanks again!




If the carb is moving 1/2" is there a problem with the engine
mounts? Maybe even flywheel out of balance, or a misfire? That
sounds like an awful lot, a 4-cyl. or greater engine at 3600 RPM
should not be moving that much IME. Probably hard on the
coupling between engine and generator too.

nate

The generator has a one cylinder, 14 HP engine. The overall
excursions, as I 'guesstimated' in my prior comment, are maybe 3/8
to 1/2 inch peak to peak, which is basically oscillating about
3/16 to 1/4 inch in each direction. The vibration has been about
the same from original installation to the present time, so I
don't think that the motor mounts have worn appreciably. It is
possible that the mounts may have a problem from the factory
which I and the Generac technician who serviced the unit under
warranty may not have noticed.

The bellows have about a half an inch of expansion and contraction
space and would appear to be adequate to deal with the vibration
in terms of lateral 'play'. There are no specs or other
adjustments, calibrations, or measurements published for any of
this.

Perhaps the one cylinder engine explains why there is more
vibration taking place than you originally expected for a 4
cylinder design?

I confused, which model Generac standby unit has a one cylinder
engine and who manufacturers the engine. The reason I ask is that
I've never seen a Generac automatic standby gen-set with a single
cylinder engine built in the last 10 years. Back in the 1990's, I
installed a number of 8kw Generac automatic standby systems that
had the Vanguard V-twin Brigs&Stratton engine then in 1999 Generac
developed their own V-twin for the home and RV gen-set market. The
last Generac system I installed was several years ago and it had
the big honkin Generac V-twin. Somebody has even built a chopper
powered by one.

http://www.youtube.com/watch?v=C6hWtuVepDU

Of course, I reread your post and it doesn't say yours is an
automatic system or the kw rating. I've serviced single cylinder
automatic units but they weren't Generac.

TDD

Thanks Nate. My Generac is described at this link:

http://reviews.northerntool.com/0394...ort=rating&dir
=a sc

It is an extremely popular and highly rated unit. Home Depot and other
places sold (literally) hundreds (possibly thousands) of these in the
aftermath of the October ice storm which devastated the Northeast area
I live in a few years ago.

This one cylinder model, at 14.5 HP, makes 7KW of electricity, plenty
adequate for a smaller home.

You will see the reference to one cylinder in the link.


In case you have trouble with the prior link I stated above, here is a
shorter link to the same page:

http://tinyurl.com/268lhp3


Now I see it, I didn't keep up with what Generac was doing with their
own engines. The problem I've been having with the old Vanguard engined
8kw units is the oil pressure switch, I've had to replace dozens of the
darn things.

TDD

http://www.gasoutdoor.com/details.asp?id=19775



Now that those of you with the patience to read this far know and
understand my predicament, I am posting here with the following
questions:


1) Frankly, at $5 per it's no exactly a bank breaking repair.

2) That said, from the picture is looks like it could handle a LOT of
vibration and relative motion between the carb and the air filter. I don't
think a simple hose would work or, worse, it would transfer too much force
between the two parts and damage one or the other.

3) and THAT said, since it connects the carb with the air filter, it would
operate with a slight negative pressure. You might try "repairing" an old
bellows or rein-forcing a new bellows with "liquid latex on the OUTSIDE.

You also might want to see whether the engine mounts are all sound. But it
looks like the vibration is sort of built into the design.

On Thu, 22 Jul 2010 00:12:47 +0000 (UTC), "Smarty"
wrote:

I personally installed a Generac natural gas stand-by generator 5 years
ago, after a freak October ice storm knocked out electricity in this
area for nearly 2 weeks.

The Generac has worked flawlessly over the last 5 years, including the
weekly exercise it does to ensure integrity, except for one HUGE
problem:

Every year or so, a $5 rubber part which Generac calls a "bellows"
ruptures without warning, leaving the generator totally unable to start
/ run.

This rubber bellows is nothing more than 2 inch long corrugated and
flexible connector which provides a flexible hose connection between
the carburettor air input and the air filter's air output. Once it
ruptures, the air/fuel ratio is grossly changed, and the engine will
neither start nor run. The rupture is not especially visible, and only
has to be the size of a pin-prick to spoil the mixture and prevent
combustion.

Generac uses a flexible coupling of this type to absorb vibration which
the engine and attached carburettor create, and dissipate it and
isolate it from the separately mounted and isolated air filter, which
sits in an adjacent chamber next to the engine.

No doubt the heat and vibration of the engine do a real job on this
rubber part, and I have been replacing them as they fail, only to have
the replacement fail less than a year later.

I spoke with Genrerac's local parts distributor, and then with a
factory Generac parts manager, hoping to find a replacement part with a
better life expectancy. When the first one failed during the warranty
period in the 10th month, I was told by the Generac service technician
that this was a common problem, and that Generac has issued a newer and
better bellows to fix the problem. He assured me that I would NOT see
this happen again.

He lied, or was ill-informed...... I am now on my 4th one, and was told
today by Generac that there are no new or replacement alternatives they
are aware of.

The one and the only part they sell to do this job can be seen at:

http://www.gasoutdoor.com/details.asp?id=19775



Now that those of you with the patience to read this far know and
understand my predicament, I am posting here with the following
questions:

1. Are there any high-temperature hose materials which can withstand
the engine compartment temperatures and vibration which I might use
instead, which would allow me merely to make a direct 2" long
connection? The ID of the hose is 1.5", and should be a pretty
standard, easy-to-find size.

2. If I use a replacement coupler which has the flexibility of a
"bellows" to allow it to dissipate vibration in the same manner as the
current part, are there other flexible couplers which exist which would
allow a more permanent / durable connection?

3. If there are no superior parts to be purchased because options 1 or
2 above do not exist, is there a 3rd option to treat this rubber
bellows in some manner to strengthen it and make it far less vulnerable
to heat and vibration?

Presumably somebody must make a flexible coupler for 1.5" diameter
connections which can take the heat and vibration better than this $5
rubber part.

To avoid digressions, I want to point out here at the onset that the
Generac is otherwise working properly, the engine is not vibrating
excessively, the temperatures are not rising excessively, and the usage
is extremely light, nearly all of it being the weekly check-out
self-test. Unfortunately 10 months of self-test seems to be enough to
destroy this part. I am very much aware that replacing this part on a
preventative maintenance schedule every (let's say) 9 months would
quite possibly solve the problem, but I am really not interested in
doing so if there is some reasonable alternative, even if the part cost
is much, much higher.

I am open to any ideas and suggestions, and much appreciate your time
in reading this, and possibly replying. Thank you very much.


Have you observed this with the engine running. Perhaps the intake
pulses induce an oscillation in the bellows causing a fatigue crack.

John Gilmer wrote:



http://www.gasoutdoor.com/details.asp?id=19775



Now that those of you with the patience to read this far know and
understand my predicament, I am posting here with the following
questions:


1) Frankly, at $5 per it's no exactly a bank breaking repair.

2) That said, from the picture is looks like it could handle a LOT
of vibration and relative motion between the carb and the air filter.
I don't think a simple hose would work or, worse, it would transfer
too much force between the two parts and damage one or the other.

3) and THAT said, since it connects the carb with the air filter,
it would operate with a slight negative pressure. You might try
"repairing" an old bellows or rein-forcing a new bellows with "liquid
latex on the OUTSIDE.

You also might want to see whether the engine mounts are all sound.
But it looks like the vibration is sort of built into the design.

Thanks for your comments John. The $5 cost for the part is really
irrelevant. The frequent failures and the resulting loss of confidence
that this standby generator will truly work in the rare occasion when I
really need it are the big issue. And finding a way to avoid having to
replace this part every nine or ten months is the mission I have been
on here.

What I have (finally) learned is that the Generac "Master" technician,
sent out during the warranty period from a very old and established
Generac dealer in this area, made 2 huge mistakes.

The first mistake was to assume that the $5 rubber bellows was at fault
due to a defect in manufacture, telling me that a newer, improved part
was being installed. The folks at Generac tell me this was not true
whatsoever.

The second mistake, and the crucial one, was that this same technician
made no effort whatsoever to see *****WHY**** it failed. I now see,
having taken apart and photographed the parts, and getting excellent
help here on this newsgroup, that the rubber bellows was being
distorted quite severely at rest, making it pre-loaded and distorted.

It turns out that there are some slotted adjustments to move one end of
the assembly around, thus allowing for correction of the misalignment.

This slotted alignment set-up is NOT mentioned in the owners manual or
the service manual. The technician apparently did not know that there
was an adjustment, and replaced the broken bellows with another one,
which then failed once again in less than a year. Had the root cause
been identified, I would have been spared all of the subsequent
replacements, all of which I have performed, assuming that the rubber
bellows was somehow weak or defective.

I briefly did install a "hump hose" made of silicone, before the
misalignment and adjustment option was discovered, and it appears that
this may have also "solved" the problem by providing a stronger
connection. But as others have pointed out here, and I observed, the
use of a hose, especially a stiffer and less compliant hose, transmits
a lot more vibration into the remaining parts, and is not an optimal
solution.

I think I have this problem solved, but the real test will be if I have
no further issues for the next several years. Other owners seem to be
getting very good reliability, and I hope to join the happy users now
that this is resolved.

This newsgroup has been an invaluable resource to me, and I am
sincerely very grateful for the really outstanding suggestions and
guidance. Thank you !!!

Lost meat from freezer: $475
Grandpa stroke, cost of ambulance ride $600
Grandpa's night in hospital $7542.36
Lost work at home office for two days $364.24
Motel room till Generac part comes $175

Yeah, it's only five bucks.

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


"John Gilmer" wrote in message
...


http://www.gasoutdoor.com/details.asp?id=19775

1) Frankly, at $5 per it's no exactly a bank breaking repair.

On Sun, 25 Jul 2010 14:59:13 -0400, "Stormin Mormon"
wrote:

Lost meat from freezer: $475
Grandpa stroke, cost of ambulance ride $600
Grandpa's night in hospital $7542.36
Lost work at home office for two days $364.24
Motel room till Generac part comes $175

Yeah, it's only five bucks.

I guess with all that on the line you should have paid for a more reliable
unit, had it serviced more frequently, or had another spare.

On Sun, 25 Jul 2010 14:59:13 -0400, "Stormin Mormon"
wrote:

Lost meat from freezer: $475

If winter, bury the meat in the snow.

Grandpa stroke, cost of ambulance ride $600
Grandpa's night in hospital $7542.36

Largely covered by insurance.

Lost work at home office for two days $364.24

Go ice fishing.

Motel room till Generac part comes $175

Fish all night!


Yeah, it's only five bucks.

Glad the OP might have a fix with his experience and adjustments.