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Possible new toy Onan 7.5 JB


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  #241  
Old 03-13-2017, 08:17:04 PM
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Default Re: Possible new toy Onan 7.5 JB

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Originally Posted by squidtrap View Post
Just want to give a special thank you to Leon, he was generous to sent high performance wires and ends to replace my junk OEM wires.

Leon, thanks again, Ed.
It's only because your JB is a magneciter!
He has had "Real Time" experience and extended service with his set. That was generous of him!
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  #242  
Old 03-13-2017, 09:30:03 PM
Leon N. Leon N. is offline
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Default Re: Possible new toy Onan 7.5 JB

Motörhead, yes because I know those wires worked out very well on my JB and I think his machine is pretty much identical to mine. I have six left if anyone wants them.

BTW Imhave not exercised my JBfor oh, maybe 3-4 weeks now. I did check the battery float voltage today and it was 14.4 volts with a shed temperature around 15 degrees. So, I think we are all set should we loose power tomorrow. They are talking about maybe 24 inches and gusts to 50. Am toying with the idea of just switching over to JB power as my prime source for the entire day since it is suppose to be a one day event. My Jb has been getting off easy since the Blizzard of 78. Depending what happens, maybe I can snap a couple of pictures for you all.
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  #243  
Old 03-19-2017, 07:43:15 AM
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Default Re: Possible new toy Onan 7.5 JB

Johnny C- i received the o-rings yesterday afternoon, thank you again. Good thing they were taped on the paper or i would have not gotten ANY see pics.

It took 1 week for them to get 1/2 ways through N.J. Last week Leon sent wires from north of Boston and they got here in 3 days!!!!! regular mail and in about a 6x8 bubble envelope, and probably 1/2 way through heavy snow. Go figure, thats why the post office is broke, UPS would have doni it under 24 HRS. shipping ground, but 3x the price.
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  #244  
Old 03-19-2017, 09:24:57 AM
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Default Re: Possible new toy Onan 7.5 JB

Ed, I am glad they finally arrived. Sad it took almost 5 days for a standard sized envelope to go 1/2 ways across the state. A currier service could have delivered the envelope in less than 2 hour.

Interesting regarding the hole in the side of the envelope. I wonder if a dishonest mail person thought there was ca$h in the envelope since the O-rings create a funny bump. Well, at least they arrived and all there. If you need more I have 42 O-rings left of which I plan to only use 8 when I am ready to put my JB back together sometime by the year 2027.

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  #245  
Old 03-19-2017, 12:22:01 PM
squidtrap squidtrap is offline
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Default Re: Possible new toy Onan 7.5 JB

Never thought of foul play, i looked at the envelope after reading this and it IS a clean slice about 1 1/2" long. Very possible somebody took a look.
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  #246  
Old 03-19-2017, 12:33:09 PM
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Default Re: Possible new toy Onan 7.5 JB

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Originally Posted by squidtrap View Post
Never thought of foul play, i looked at the envelope after reading this and it IS a clean slice about 1 1/2" long. Very possible somebody took a look.
If it is a clean slice ( not a tear) as seen in your picture I believe without doubt the envelope was opened by someone in the postal service. Not good.
At least the "payload" is all there and in good condition.

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  #247  
Old 04-12-2017, 05:24:46 AM
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Default Re: Possible new toy Onan 7.5 JB

Been so busy no time to touch the JB.

Yesterday i wanted to finally give it a run other than just popping it over so i got my spare garretson regulator that i never tried, pulled the piping off the CCK, connected the nat gas line, and POW. it fired right away, let it run for about 20 min. 62HZ 120/240 V no load (have nothing but wires right now) did not have to adjust anything!!!!!!!!!!!!!

SO its time to start getting serious and get my azz moving soon as i get back from florida. Best 200.00 i ever spent, Ed
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  #248  
Old 04-12-2017, 08:27:45 AM
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Default Re: Possible new toy Onan 7.5 JB

Ed, sounds like a home run. good to hear that everything is ok.

Bob
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  #249  
Old 04-29-2017, 04:10:22 PM
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Default Re: Possible new toy Onan 7.5 JB

SO, had a little time today to work on the new JB, cut and installed the new plug wires that LEON was so generous to donate to me, they work great, very hot spark, (thanks leon) and installed new plugs and gaped for nat gas.

took off mag cover and blew out w/ compressor and ensured brushes were free, all was good and rings were perfect, almost looked new, just a light brown glaze.

Greased end bearing and removed old grease, (really probably did not need it, grease looked new and fresh)

wanted to flip over to gen power w/ air running but by then wife came home and immediately shut OFF air, she is a reptile, loves the heat, so that was it for the day, had to do the wife thing and heading to concert tonight so tomorrow is another day.
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  #250  
Old 05-22-2017, 06:00:23 PM
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Default Re: Possible new toy Onan 7.5 JB

Finally got my compression tester back and checked the JB. both cylinders are 130 on the button, guess that is good.

Figured while i had time and never checked my 5.0CCK (factory vapor set) i would and it was 150 on both cylinders ? Does not seem very high for a vapor set, anybody know what it should be w/high compression heads?
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  #251  
Old 05-22-2017, 06:22:18 PM
Kevin K Kevin K is offline
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Default Re: Possible new toy Onan 7.5 JB

When I tried a set of high compression heads on my 5CCK, they were 145PSI on both cylinders, compared to 110PSI with the standard heads. So yours seems to be in the ballpark. I decided that was a bit high if I intended to ever run regular gasoline again, so I reinstalled the standard heads. Maybe I will give it a try again with two head gaskets to get the compression down a bit. About 135PSI would be great to run either propane or gasoline.
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  #252  
Old 05-23-2017, 05:13:46 AM
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Default Re: Possible new toy Onan 7.5 JB

Thanks Kevin- CCk will only b ran on nat gas. I guess that is high then.

Also glad to see 130 on both cylinders of the JB considering the age. What tanks they built back then.
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  #253  
Old 08-12-2017, 07:35:23 PM
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Default Re: Possible new toy Onan 7.5 JB

So, today was the first time i had a chance to run the JB w/ load for any amount of time. with no load set hz to 63 and they were jumping around quite a bit, 59-63 put about 3000K on it and it was hunting quite a bit. With no load hunting was not noticeable, just fluctuating quite a bit.

The book says dial in HZ w/no load then fully loaded adjust governor to eliminate hunting. Played for about 3 hours and its a real PITA. Even with about 3000K cant seem to eliminate hunting.

Any tips on getting it dialed in? and is it possible the governor spring can wear out?

I adjusted the sensitivity ratchet but really makes no difference, just more and more adjusting of speed nut and ratchet.
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  #254  
Old 08-12-2017, 08:35:09 PM
Leon N. Leon N. is offline
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Default Re: Possible new toy Onan 7.5 JB

Squidtrap I feel your pain. I had a hunting problem at around a 1500 watt load. No hunting above or below that load. So after discussing on the Stak, I tried the suggestion to raise the NL speed to 61.5 Hz. That seemed to cure the 1500 watt hunting. I maybe wrong but I assume my flyball governor cup has a worn groove and now the flyballs are spinning on a unused surface.

I can meet the specified frequency droop of 5% (3 hz) with a one step application of ~ 4000 watts. I cannot meet the recovery spec of 2 seconds, however. Working on that. Just got a new compression tester and will report under another thread the results. BTW, these manuals list the compression pressure for both the low and hi comp designs.


I am about to try out a suggestion of tweaking the idle gas jet at NL to get rid of an occasional popping back in the carburetor. I can eliminate this popping by enriching the main gas jet but then it falls out of the 5 % tolerance.

I do not think the governor spring can wear out, but how it is installed and adjusted is very important.

Basically I followed the governor set up procedure spelled out in 967-320 or was it 967-500. You should have both manuals. If not let me know.
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  #255  
Old 08-12-2017, 11:34:14 PM
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Default Re: Possible new toy Onan 7.5 JB

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Originally Posted by squidtrap View Post
...I adjusted the sensitivity ratchet but really makes no difference, just more and more adjusting of speed nut and ratchet.
Hmm.. Really - the sensitivity setting make no difference in the hunting? Seems like an odd thing. It's a pain to adjust, and interacts with the governed speed, but you ought to be able to go from wild hunting, to sluggish governor response as you run that sensitivity screw to its two limits.

One thing that might help - open the idle gas screw (this is NG-powered, right?). It doesn't make a huge difference, but I have seen it help. On my JB, even opening the idle jet full open isn't 'too much'. To set the main screw, I just apply max load (usually 7 kW or so) and tweak for max speed.
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  #256  
Old 08-12-2017, 11:49:21 PM
Leon N. Leon N. is offline
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Default Re: Possible new toy Onan 7.5 JB

Take a look at the picture I submitted in post # 46 under my thread entitled A JB Performance Question and tell us where on your JB governor shaft, the spring is attached. Maybe that would tell us something if your spring was attached in an unusual place thus making it harder to tweak in. Not sure but would be curious what your set up looks like. Also, what is the factory spec your JB was built too? Onan has two governor adjusting procedures you must piick the correct on depending on your model factory revision.
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  #257  
Old 08-13-2017, 06:43:57 AM
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Default Re: Possible new toy Onan 7.5 JB

i think later im going to switch regulators from my cck to the JB. i know the cck is good.

If no luck i will try your ideas jim, main thing is getting it to run stable no load or medium load (bad hunting at medium)

Leon- i went over both manuals on governor setting and did exactly what they said. as far as the spring goes it moves with the ratchet screw up or down, its on the threaded part of governor rod.

Need to figure what makes the hunting go away, more or less sensitive, they say less???

Leon-my spring is now about where yours is, about 1/2 way up the threads, but did not run it sense. You have the other adjustment where all is done from the nut on the blower housing, mine is spec s so i have the hole on the side to adjust the ratchet which moves the spring. PITA

Last edited by squidtrap; 08-13-2017 at 07:36:57 AM. Reason: info
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  #258  
Old 08-13-2017, 08:10:41 AM
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Default Re: Possible new toy Onan 7.5 JB

Ed, it sounds like a fuel problem to me when your demand regulator droops the governor is doing its job trying to keep up

Bob
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  #259  
Old 08-13-2017, 08:15:47 AM
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Default Re: Possible new toy Onan 7.5 JB

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Originally Posted by squidtrap View Post
i think later im going to switch regulators from my cck to the JB. i know the cck is good.
yes do this. sounds like a fuel problem to me.
are you using natural gas or propane?

If propane, what size tank?
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  #260  
Old 08-13-2017, 08:55:23 AM
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Default Re: Possible new toy Onan 7.5 JB

Bob- as i think more about it im going to switch regulators first. starts and runs fine w/ no load but w/ small load thats where the problem starts.

Scoops- nat gas, other gens run fine. plenty of gas, leaning more toward regulator.

Leon-spec S
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