Lawrence Show full post »
Lawrence
I sincerely appreciate the guidance and comments, and will continue to monitor this thread.

I have had a local Master Dealer service my unit, and the "Certified Technician" dismissed the issue as being defective bellows. Supposedly the replacement part is thicker and more durable, and less likely to fail from abrasion.

Since I have had the first one replaced under warranty for free and the second one replaced at my expense around the end of the 2nd year of ownership, I am reluctant to pay for another service call, only to be "promised" that the newer repair part solves the problem. It certainly did not solve the problem yet based on the continuing need for me to put a new bellows in a 3rd time. The rubbing is very obvious, yet the Generac technician called the problem a "defective bellows" replaced with a better design.

Since ohmslaw has partially answered my question, I know now that some 7KW units have run without this problem for extended periods of time. I have to believe that they are using the same, improved bellow part that I am. I also have to believe that they do not have a constant crushing and rubbing of the bellows against the breather hose, and thus do not fail like mine does.

I am left with the mystery of what repair or part replacement can be performed to eliminate this problem. If necessary, I will resort to the techniques proposed (grease, taped together parts, fabricated bracket, etc.), but I would sure love to know if there is some other way to solve this which fixes the original problem / misalignment properly.

Many thanks again!
Larry
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ohmslaw
You need to verify that the engine mounts are intact and that the engine is running smoothly. The only culprits I can see here are excessive vibration or a misaligned air box . I would think there is a setting between grossly misaligned and not rubbing
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Lawrence
Thanks ohmslaw! The air box can be moved far enough on the slotted holes to eliminate contact between the bellows and the breather hose. The adjustment puts the air box at the extreme end of travel of the adjustment.

When I make this adjustment, the bellows no longer have slack and are stretched out. The input and output ports of the bellows are visibly no longer aligned, and the bellows is on a distorted path, no longer horizontal. The one end of the bellows is (I am guessing) 1/4 inch or 3/8th inch higher than the other end. Yes, the bellows now clears the breather tube, but it looks like it is way out of proper alignment, and also is preloaded to the extent that it probably cannot absorb the vibration and shock correctly.

There is no setting of the air box position which offers an interference-free, non-rubbing bellows position except for the extreme positioning I have described above.

Regarding the motor mounts and vibration, I have taken videos of the engine under load and watched the bellows. The vibration seems to move the whole assembly around maybe + and - 1/8 to 3/16th of an inch, possibly 1/4 inch. This does not seem to be excessive (for a single cylinder engine) and I would imagine that the bellows can easily tolerate that type of oscillation without any problem if it isn't rubbing against something which is also crushing the pleats of the bellows.

I don't know if there is a better and more accurate way to assess the vibration issue.

I began with the assumption that the problem arises not because the vibration is excessive but rather that the adjacent rubber parts should NOT BE RUBBING AND COMPRESSING EACH OTHER, and I sure would like somebody with a 7KWH generator who could tell me whether it is typical for these parts to be touching as mine do, with the pleats of the bellows collapsed on one side.

I welcome any more suggestions here about how to evaluate the motor mounts more correctly.

Many thanks again!

Larry
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ohmslaw
Larry,
Without movement the bellows will not wear out. How many hours is your unit running each year. I can not imagine that the exercise time is enough run time to wear out the bellows. I would set the air box in the middle of its travel, not stretching the bellows tight but relieving the pressure. There are to many of these in the field working properly to attribute the wear to the proximity of the tubes. I would focus on excessive vibration or movement.
Tim
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Lawrence
Thanks Tim!

I did leave the air box in the middle position of the slot based on the same reasoning you stated. My Generac ran a total of maybe 14 hours in addition to the exercise periods, which I would estimate to be another 10 hours or so, for a total of 24 hours. Whether this is enough running time to wear a pinhole in the bellows is hard to say but does seem awfully short.

I wonder if there is any way to accurately determine if the motor mounts or other vibration related parts are defective or out of adjustment?

Thanks again!
Larry
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murphy
I discovered last week that the bellows on my 7K has deteriorated very badly. It has a severe bend from contact with the rubber tube and has a rupture in that area. The generator is 5 years old and has 66.8 hours on it. According to my records the crank time began increasing in March 2010. When new it fired immediately. Now it cranks for 3 to 4 seconds before it fires. I was aware of the firing delay but never took the time to investigate.
I presume the starting delay is caused by the propane gas leaking out of the piping from the gas valve to the bellows. They made a big deal over locating the propane tank at least 10 feet from the generator. Now it turns out propane has been leaking inside of the cabinet for over a year.
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Lawrence
I am not alone !! ??

My 7K unit is about the same age and usage as yours, murphy, but I am going through bellows at a faster rate. Your bellows is probably the original, weaker design which they improved 3-4 years ago.

The leaks and longer cranking time was exactly what I encounteted. Eventually the weekly exercises will fail entirely after cranking cannot start the unit due to bellows leaks.

I would suggest a new replacement bellows and a carb adjustment.

Does your bellows stay in contact with / rub against the breather tube?

Larry
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murphy
Lawrence;10782 wrote:
I would suggest a new replacement bellows and a carb adjustment.

Does your bellows stay in contact with / rub against the breather tube?

Larry


The new bellows is scheduled to be delivered tomorrow.

There is about 1/4" of interference between the bellows and the hose.

I'm going to try putting spacers on the air cleaner mounting bolts to move the air cleaner back and see if I can get more clearance between the hose and the bellows.
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Lawrence
murphy,

I have about the same 1/4" interference as you do. I tried moving the air cleaner but I then wind up with an elongated bellows which no longer absorbs the vibration from the engine nearly as well. My "solution" has been to replace the bellows each year when I do the preventative maintenance oil change, spark plug change, air filter change, etc.

You may find that the newer, thicker bellows holds up well enough that the problem is now solved. Your original bellows lasted 5 years whereas mine had failed in less than a year, as did the subsequent replacement bellows.

Good luck and please let me know how the spacers work out. I only used the slotted holes to move the air filter to a different position but I never did tried using spacers.

Larry
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murphy
The new bellows finally showed up today, USPS tracking said it would show up last Friday. It is of much sturdier construction than the original.

I abandoned the spacer idea when I realized it wouldn't change the spacing between the bellows and the bend in the rubber tube.

I put my Rube Goldberg hat on and modified the rubber tube. I cut 3/4" off of the air cleaner end with a sharp knife (do not use a saw). I then cut the tube half way between the engine fitting and the bend. I installed the 3/4" piece at the location of the cut in the tube using high pressure tape. The result is that the tube is the same length but the bend is 3/4" closer to the air cleaner. The bellows is close but does not touch the rubber tube. It's not pretty but it works. If you are not sure of your cutting and fitting skills I recommend having a spare tube on hand before you try it.
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genme
murphy, are you able to post a picture of your work? It would be most appreciated.
Model 5875, Nexus controller, 999cc Engine, 20kW LP, 2011
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murphy
I attached two photographs to this message.
:)
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genme
Thanks!
I know you said "high pressure tape", but all I see online is bicycle rim tape. Can you tell us more about the tape you used?
Model 5875, Nexus controller, 999cc Engine, 20kW LP, 2011
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murphy
genme;10925 wrote:
Thanks!
I know you said "high pressure tape", but all I see online is bicycle rim tape. Can you tell us more about the tape you used?


It's called Magic Wrap. It's made by Glasgow Manufacturing of London, Ontario, Canada and Erie, PA. It's water tight and air tight to 100 psi. It's rated for 0 to 212 degrees F.

[url]http://www.glasgowmfg.com/pages/magicwrap.html[/url]

I got it at Lowe's several years ago but they appear to have stopped stocking it.
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Lawrence
murphy,

Your solution is EXCELLENT and totally solves the interference problem. I must wonder why Generac did not design and make a molded hose with the correct dimensions in the first place, but this certainly solves the rubbing / wear problem.

I am going to order another replacement hose from Generac (maybe 2) and cut them and tape them as you have done. Perhaps I will THEN FINALLY have a reliable generator......

It is extremely satisfying for me to finally discover that I am not the only 7K owner with this problem. It has been at least a year and a half since I started this thread, and up until recently I could not find a single owner among the many many 7KW users who seemed to have the same issue I have been having. I gotta' wonder how many other owners have startup and stalling and other failures which are directly a result of this very poor design.

Many thanks again murphy,

Larry

BTW, your photos are excellent. You take pictures like a pro!
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