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Onan Generators

Onan 7.5 JB-3CR31/9286T


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  #41  
Old 08-13-2015, 11:26:43 AM
nothingbutdarts nothingbutdarts is offline
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Default Re: Onan 7.5 jb-3cr31/9286t

Nice oil temp. gauge Leon!
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  #42  
Old 08-13-2015, 11:36:42 AM
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Onan Dan Onan Dan is offline
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Default Re: Onan 7.5 jb-3cr31/9286t

Leon you are right the motor mounts are to snug I will loosen them up a little
they got to have some motion movement that will help .yes that is a neat oil temp gauge you have on your JB. thx
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  #43  
Old 08-13-2015, 02:00:59 PM
Leon N. Leon N. is offline
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Default Re: Onan 7.5 jb-3cr31/9286t

Ah yes, that oil temp gauge is no longer necessary. It has never gone above 250 degrees F. That was installed way back when I had to change the oil twice a year in order to comply with the Onan requirements. Since then, the lubricating oils, specifically the synthetics permit me to change the oil, oh maybe once every 3-4 years based upon my use profile. I use a low viscosity 5W20 synthetic all year round. It has excellent cold and hot temperature lubricating properties, with the high end at around 400 degree F.

I use the same oil in our Camry which now has about 225,000 miles or about 5000 hours equivalent operating time. My JB has about 1500 hours so far.

Dan when ever you start your JB you should let it run long enough to get the oil hot so as to drive out moisture. Also use you fingers to touch that oil line running to the valve chamber to make sure it is also getting hot, which is an indication that the line is not plugged. That oil line which runs behind the ignition breaker point box is necessary to provide lubrication and cooling to the over head valves.
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  #44  
Old 08-13-2015, 05:15:46 PM
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Onan Dan Onan Dan is offline
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Default Re: Onan 7.5 jb-3cr31/9286t

Thanks Leon you have answered another question I was going to ask you oil wt# I saw the oil line running up to the valve chamber next time I run it I will check for hot line the other day I started it for a couple minute and shut it down and I could hear oil draining back down to oil pan that synthetic oil is the way to go what a bout mobile 1 synthetic oil wt 5w 20 ? also what oil filter the service manual someone wrote in Purlator Per 17 for filter .the oil is really clean at this time probably will not change it for a few hours run time on it also points and condenser I found the onan numbers but not sure what they are ? Leon I did loosen up the motor mount bolts they were too tight I just ran the nuts down to touch by finger and used blue locktite on threads so they do not get loose try it and see what it acts like when I get it in position I think I will set it on 4x4 treated wood that will help take shock off my garage floor sure appreciate your help .OD
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  #45  
Old 08-13-2015, 10:17:12 PM
Leon N. Leon N. is offline
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Default Re: Onan 7.5 jb-3cr31/9286t

Dan, I have been using Mobile-One 5W20 full synthetic for a number of years now. I have changed the oil once about 5 years ago. Burning natural gas results in very little contamination of the oil. It remains very clean especially when compared to burning gasoline. If one has the option, I would always prefer gaseous fuel over gasoline for other reasons as well.

One thing you should be cognizant of is water getting into the oil. The only way to minimize or even prevent this is to fully warm up the plant each time it is started- and do not employ and heaters like a cc heater of a strip heater inside the cooling plenum.

As for oil filters, I have used in the past, Fram PH16, Wicks 51084,Hastings P126 or Mobil 1 M1-204.

Pretty soon I will be changing the oil after some 4 or 5 years and will submit a sample for analysis, just as a curiosity. The synthetic tends to ooze out in some areas, but I do not worry about that because this JB uses very little oil.

On my JB mounting. I mounted two 4 x 4's on four 5 # coffee cans. Filled them with cement with a long bolt protruding upward to secure the 4 x's. Then I mounted the JB on the 4 x's by drilling for the Onan through bolt that holds the rubber cushions. You can sort of see this in my picture.
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Old 08-14-2015, 07:27:52 AM
Max Thompson Max Thompson is offline
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Default Re: Onan 7.5 jb-3cr31/9286t

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Originally Posted by Leon N. View Post
Dan, if you received the JB mouthed to that metal frame as shown in your first post, I would say, that is OK. All you have to do is secure that metal frame to the floor.
If you will set the mounting skid on top of some 8" concrete blocks, it will make servicing a little easier. As Bruce reminds us, getting it up about 16" off the floor makes it much easier for "ageing" owners to work on the set.
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  #47  
Old 08-14-2015, 07:31:12 AM
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Default Re: Onan 7.5 jb-3cr31/9286t

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Originally Posted by Max Thompson View Post
If you will set the mounting skid on top of some 8" concrete blocks, it will make servicing a little easier. As Bruce reminds us, getting it up about 16" off the floor makes it much easier for "ageing" owners to work on the set.
Thanks Max I know what you mean the ole body seems to be getting non flex able any more .
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Old 08-14-2015, 09:12:00 AM
Leon N. Leon N. is offline
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Default Re: Onan 7.5 jb-3cr31/9286t

Yes, it is a good idea to have access all around your machine. However, I must point out it might be better not to mount that metal frame directly on cement blocks, but to put a board or something like that between the metal and the cement block. And how does one envision securing the cement blocks to the floor?

In my situation, I have a chain fall hoist hanging directly above the JB. Not by design, but it was given to me way back when I installed the JB. In 40+years I only once had to use it to raise the JB, rotate it 90 degrees to gain access to the starter.

Knock on wood, this JB magneciter running on NG and lubed with Mobile 1 5W20 full synthetic, housed in a dry shed, is very reliable and will out last me. This is one tough puppy.
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Old 08-14-2015, 05:45:44 PM
Max Thompson Max Thompson is offline
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Default Re: Onan 7.5 jb-3cr31/9286t

Quote:
Originally Posted by Leon N. View Post
Yes, it is a good idea to have access all around your machine. However, I must point out it might be better not to mount that metal frame directly on cement blocks, but to put a board or something like that between the metal and the cement block. And how does one envision securing the cement blocks to the floor?
Leon is correct about not mounting metal directly to a "hard" surface. Like Dan mentioned, I used some 3/4" rubber stall matting on top of the blocks ( I only went one block high). I did not anchor the skid to the blocks or the floor, it has been in the same place for several years with no movement. I have considered some all-thread anchors, in the event of a tornado, it might keep the JC in my yard & not in Kansas.
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Old 08-14-2015, 06:52:04 PM
squidtrap squidtrap is offline
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Default Re: Onan 7.5 jb-3cr31/9286t

Dan- i would do like Leon said but use some of the mining belt under the metal frame for noise suppression. The mining belt is like conveyor belting correct ? you could also put it on some 4x4 to raise it up for working height.

Put the belt on floor, 4x4 on top, Gen on top of that. Wish i was in your boots right now. Such troubles,problem is you dont even need to tinker with it. Just plug and play, oh yeah, you need a bigger load bank.

.
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  #51  
Old 08-14-2015, 06:52:17 PM
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Default Re: Onan 7.5 jb-3cr31/9286t

I used crossties . Shot the skid to them with lag bolts.
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  #52  
Old 08-14-2015, 07:23:45 PM
Leon N. Leon N. is offline
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Default Re: Onan 7.5 jb-3cr31/9286t

Here are a couple of pictures of my JB installation inside the shed. I cemented four coffee cans into the floor with bolts protruding to hold the 4x's. Then I sat the JB on the 4 x's. I prefer to have the center of gravity of the JB close to the floor, obviously more difficult to work on, but then again I have had little or no need to work on the JB after installing it. I also oversized the exhaust system using 2 inch IPS and located the muffler inside to prevent rusting. The flex section was of stainless steel and I recall the manufacturer stating not to put any rotational stress on it. The entire exhaust system is supported by a hanger to take the weight off the JB exhaust manifold. I have a chain fall handy but I have only had to use it once in 44 years to gain access to the starter. Points, plugs, timing marks, etc are easily assessable from the near side.
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  #53  
Old 08-14-2015, 07:59:46 PM
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Default Re: Onan 7.5 jb-3cr31/9286t

Real good idea to have a tight shed like Leon has, that tends to temp stabilize it and keep it dry. Here heavy metal outside gets soaking wet with condensation in warm humid spring mornings after cold soaking all night.

Another nice advantage of a wood shed is easy to put a wood or I-beam across to hook chain fall to. 2x4 or 4x4 for vertical supports and nail to shed so it doesn't fall sideways or buckle. If shed is weak will need to diagonal brace beam and verticals.

Dad had beam in garage to lift car engines, used a removable 2" pipe to floor to help support beam over long span. When tenant removed ceiling recently turned out the beam was a 20ft section of a tree. Tapered beam and dry split down the middle after 65 years.

Last edited by len k; 08-14-2015 at 11:29:56 PM. Reason: temp stabilized, tappered beam
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Old 08-15-2015, 06:34:46 AM
b74eqcm b74eqcm is offline
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Default Re: Onan 7.5 jb-3cr31/9286t

Another option is to get it up higher, making it easier to work on. (my knees aren't what they used to be) In this thread are pictures from the installation of my 12.5 JC. I built a taller stand to mount the generator on. Just an idea.

See: http://www.smokstak.com/forum/showthread.php?t=134944

jim
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Old 08-15-2015, 09:07:54 AM
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Default Re: Onan 7.5 jb-3cr31/9286t

All good ideals everyone I have an engine hoist and I can lift the JB easy enough I think I will put down heavy rubber belting on concrete for damper on concrete and mount treated 4x4 to JB frame and set on rubber belting and then drill concrete and bolt down through the 4x4 with anchor bolts it will stay in place. Fellows one thing a bout it we have a big blow we can just tie our selves to the JB it will hold us down I still can not believe the size and weight it has . Thanks OD
Talked to my Uncle he said do not put rubber belt on concrete that is just something to cause the stud maybe to loosen out of concrete he said use the lead anchor bolts drill part way in to concrete and bolt 4x4 down the rubber motor mounts will be enough movement sounds good to me.

Last edited by Onan Dan; 08-15-2015 at 10:05:29 AM.
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  #56  
Old 08-15-2015, 11:04:43 AM
len k len k is offline
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Default Re: Onan 7.5 jb-3cr31/9286t

I agree with no rubber between pressure treated wood and cement floor. No reason to allow motion there, you want a solid connection, cement is brittle. Let the JB's rubber vib mounts take all the motion.

JB is very heavy, ~ 475 #. Up side is no one will walk away with it.

For my old knees I use a 2.5 inch thick plastic foam pad that came with some shipping box. I can drop to my knees on it and not bottom out or hurt.
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  #57  
Old 08-17-2015, 08:33:26 AM
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Default Re: Onan 7.5 jb-3cr31/9286t

Got to get back on this JB this week need to go to town and get bolts to mount it on 4x4 and to the concrete Sqidtrap [ED ] post a picture of the paint you touch up your onans with if you could some time the paint I use is to dark green got two spots want to clean rust and touch up leave as natural as I can like the old patina it shows like me I am weathered THX
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Old 08-17-2015, 08:28:59 PM
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Default Re: Onan 7.5 jb-3cr31/9286t

This JB has a Champion spark plug H-10 hope I can get a couple of them when I go to town? what plugs do you run in your JB 7.5? The H-10C is a copper core how would that be if I can not get the H-10?
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  #59  
Old 08-17-2015, 08:43:41 PM
David C David C is offline
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Default Re: Onan 7.5 jb-3cr31/9286t

I am pretty sure you can only get the copper core plugs.

David C.
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Old 08-22-2015, 01:02:31 PM
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Default Re: Onan 7.5 jb-3cr31/9286t

Got the JB metal frame fasted to the 4x4 cross beams and anchor bolts thru the 4x4s to the concrete floor and the motor mounts are loosened up so there is lateral movement it is setting out there running like a champ much better now .
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