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Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

A Bad Onan kind of day!


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  #11  
Old 04-11-2017, 01:01:28 PM
len k len k is offline
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Default Re: A Bad Onan kind of day!

Buy Flight systems standard 305 model and it's only ~ $225 , but mounting is slightly different.
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  #12  
Old 04-12-2017, 08:00:08 AM
GMGuy GMGuy is offline
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Default Re: A Bad Onan kind of day!

Thanks for the info guys.
I will clean the rings this weekend and then determine if its good or not. I also picked up NGK B6L plugs for my JB, as I am not a fan of Champion. I have not looked at the current plugs, but it is the cheapest place to start.
Ralph

I should also do an oil change on the JB, what filter number is used on the 7.5 JB?

Thanks in advance, you guys know everything!
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  #13  
Old 04-12-2017, 02:34:30 PM
Vanman Vanman is offline
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Default Re: A Bad Onan kind of day!

Might want to try checking / changing the points and condenser on the ill running JB. Had a condenser giving me fits before. It "tested" good with ohmmeter and a capacity meter, but was shorting out under actual operating voltage. I tried a new one "for the heck of it" and away she went!!
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Old 04-12-2017, 07:24:13 PM
dracer dracer is offline
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Default Re: A Bad Onan kind of day!

Quote:
Originally Posted by Vanman View Post
Might want to try checking / changing the points and condenser on the ill running JB. Had a condenser giving me fits before. It "tested" good with ohmmeter and a capacity meter, but was shorting out under actual operating voltage. I tried a new one "for the heck of it" and away she went!!
through the years I have found , the onan condensers go bad a lot
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  #15  
Old 04-13-2017, 06:20:03 AM
GMGuy GMGuy is offline
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Default Re: A Bad Onan kind of day!

I will start with plugs this weekend, and while they are out, I will take a look in the jugs. If that does not get her to run, I will ensure I have spark and then go to carburation after that. I will let the group know how I make out.
I will certainly be distracted as it is ATV season, and I need to get my docks and boats in (if the ice is out....).
Thanks for the tips!
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  #16  
Old 04-13-2017, 07:02:25 AM
willie1959 willie1959 is offline
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Default Re: A Bad Onan kind of day!

I am at Jack lake ice was still in bay Tuesday but my area was clear. For sure next week. Ice is normal this year, normally out around April 20 which is normal. Buying propane this week for gensets at Costco price the same as last year 0.59 a liter price no carbon tax increase cool, drops all summer. Going to rebuild my 4500 onan this summer. Found a low hour motor 150 vs 3700 to due swap and ordered a new slip ring for rotor. Current motor leaks oil out fan end but runs fine.
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  #17  
Old 04-17-2017, 09:29:02 AM
GMGuy GMGuy is offline
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Default Re: A Bad Onan kind of day!

So weekend update on the 2 misbehaving Onans.

I did not even look at the Marquis 5500, seems that the beers were cold and in the way....

The 7.5 JB was my focus. I bought a set of NGK 6BL plugs and removed the possibly original Chumpions. They were nasty, one plug was crudded up right across the gap, no wonder it wouldn't run. Put the fresh plugs in and it fired right up. Seemed to be running well, then I noticed I had only put on 1 plug wire (but still was at 60HZ, I can't believe it). So, I shut it down, put on the other wire and wow, did it ever run smooth. Perhaps it has never run on 2 lungs since I got it. I ran it up to temp, and loaded it to about 3000w, and it didn't even grunt, oil pressure stayed 20-30psi.

I love this JB set. It rocks!!!
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  #18  
Old 04-17-2017, 02:03:47 PM
grif grif is offline
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Default Re: A Bad Onan kind of day!

Since being out of the orchard business,,, I kept an old MF50 with a bin lift on it. one cylinder fouls plugs after running 6 or 8 hours. I got in the habit of just swapping plugs to different cylinders every lunch break, that's got to be 20 years ago and still running just fine. The move to a clean cylinder would burn off the oil just fine.

Long version of saying, after you run it a few hours, pull the plugs to see if you've got anything going on.


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one plug was crudded up right across the gap, no wonder it wouldn't run. Put the fresh plugs in and it fired right up.

I love this JB set. It rocks!!!
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Old 04-17-2017, 02:15:06 PM
len k len k is offline
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Default Re: A Bad Onan kind of day!

When trying to start my yard plow truck in winter, I accidentally found heating the plugs till insulator is cherry red hot burns off all the oil and crud. Started right up after that.
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Old 05-30-2017, 07:49:08 AM
GMGuy GMGuy is offline
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Default Re: A Bad Onan kind of day!

Latest update from the weekend... still haven't looked at the Marquis 5500, but ran the 705 JB and it was doing fine, until.... it stopped outputting voltage. So, I stopped it and cleaned the slip rings, and then it started to produce power again.
The frequency was a bit low (about 56Hz), so I adjusted the spring and got 61Hz uploaded, but then noticed I had 307V AC
This is a Magneciter unit, so I started reading about what to check...

Hoping people can confirm, I should check the coils and Diodes, anything else? Is my Magneciter fried?
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