A $5 part *****kills***** a $4000 Generac generator

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Smarty wrote:

..snip..
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.
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chaniarts wrote:

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!
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Smarty posted for all of us...

See my other post but look at automotive CV joint boots.
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Tekkie Don't bother to thank me, I do this as a public service.

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I wonder if the OP has written Generac to let them know about the repeated failure of the bellows-duct?
Maybe they would like the failed parts for analysis and could come up with a more durable part.
the CV boot idea sounds promising;a good idea. either CV or tie rod end boot.
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Jim Yanik
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On 07/22/2010 05:02 PM, Smarty wrote:

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
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Nate Nagel wrote:

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

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
hWtuVepDU
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
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The Daring Dufas wrote:

Thanks Nate. My Generac is described at this link:
http://reviews.northerntool.com/0394/16714/reviews.htm?sort=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.
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Smarty wrote:

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

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
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On Fri, 23 Jul 2010 05:53:32 -0500, The Daring Dufas wrote:

Kohler made/makes a 15 hp single that is very well balanced and pressure lubed. MY Deere LT155 has one in it. Bought in 2000, serviced once a year (oil, filters) it runs like it did the day it was driven off the showroom floor. I could easily see a derivative of the Kohler Commander single in a standby generator. It would run very quietly though and that's one thing the OP said his didn't do. He also said it was a 7kw generator with an auto mains switch.
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Meat Plow wrote:

Kohler offers a competing standby generator to my Generac, which I will assume uses some variant of that 15 HP engine. The Generac I have here uses a Generac-built engine.
I am linking to an exploded parts drawing from the Generac service manual for the area I am discussing / working in. Not sure it adds anything useful, but it illustrates how the bellows attaches to the air filter base on one side and the engine on the other:
http://img25.imageshack.us/img25/4607/captureki.jpg
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Some good ideas in all these posts, but may I suggest one more item to look at? If the failure is due to movement between the rigid mounted air cleaner and the engine intake, find the source of the excessive engine movement, for example old tired gushy motor mounts. Seems to me if the engine/intake movement is normal, then most any common automotive hose should last for years. Good luck.
Joe
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Joe wrote:

Joe,
I would love to pick the brains of the folks who designed this thing to better understand the part they chose. I can surmise that the bellows was selected to allow for a fair amount of vibration and movement between the carburettor mounted atop the vibrating engine and the nearby stationary air filter assembly. For reasons unknown to me, they chose not to hang the air filter immediately above the carburettor as was done in classical automotive designs for many years. This would have eliminated the need for a bellows and floating connection altogether.
I am entirely frustrated by the fact that no other Google references show up with other people having this same problem. I would imagine that a complaint or two, or perhaps many more would indicate that this is indeed a design flaw rather than my own unique predicament. It tends to give weight to the theory that something else is amiss, such as the motor mounts. I am just not sure how much motion is typical of a single cylinder engine, but I certainly do not recall seeing this much play in my lawn tractor, snow blower, etc.
The bellows is made of thin rubber, no more than maybe 3mm, and possibly thinner. It is extremely tempting to put a Fernco or other flexible hose in the place of the bellows, but I do share the concern that I am now transmitting much more vibration rather than dissipating it.
I am going to call Generac tomorrow (again) and also call a local "Master" Generac service center and see if I can glean any more information.
I have posted a couple photos to show the inside of the Generac.
The first photo shows the overall internal layout with the bellows highlighted by a white ellipse. The engine and carburettor are to the left, and the enclosed air filter compartment is to the right.
The second photo is an enlarged view of the bellows area.
I did not post these earlier, since they really do not show a great deal about the specific bellows problem area. They do reveal how tight and space-constrained the area of the Generac is on the inside where the defective part is situated..
http://img408.imageshack.us/img408/1516/largegeneracimage.jpg
http://img338.imageshack.us/img338/2750/smallgeneracimage.jpg
Thanks once again to all!
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Smitty Two wrote:

Smitty,
This certainly appears to be true, and may explain my problem entirely. The other nearby hose actually lies well above the bellows and clears it with no interference, but 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.
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Smarty wrote: ...

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.
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dpb wrote:

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.
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Can the air filter be moved further away? In which case a long radiator hose with a 90 degree bend would provide the flex needed?
Or perhaps even longer and an S type hose would provide quite a bit of back and forth movement?
Or perhaps dump that air filter and go to the automobile wrecking yard and see what is available with the same size tube...
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On Thu, 22 Jul 2010 09:42:37 -0700, Bill wrote:

There should be several options. I know the space is limited inside the housing but there's got to be a better solution. Maybe look at some of the high performance auto type filtration components. That bellow/intake arrangement has got to have some type of pressure sensor that won't allow the natural gas valve to open if the bellow has a leak. That would prevent the thing from catching on fire if a leak occurred.
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One more thought. Since it is a short distance cut up a NITRAL (spelling) glove by removing the fingers and clamping remainder in place. I use these gloves in wood shop when using stains and thinners and they hold up fine. The gloves are Blue in color and I buy from Harbor Freight. WW

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