Generators and Motors
[Home] - [HELP] - [Forums] - [Library] - [Photo Gallery] - [Groups] - [Classified Ads] - [Subscribe] - [Links] - [Books] - [Sponsors] -

Go Back   SmokStak > SmokStak® Vintage Electrical Equipment > Generators & Motors General Discussion > Onan Generators
Forgot Password? Join Us!

Notices

Onan Generators Restoring, operating and maintaining vintage Onan generators.

Onan Generators

Onan JB vs JC


this thread has 33 replies and has been viewed 710 times

Reply
 
Thread Tools Display Modes
  #1  
Old 08-13-2017, 08:28:55 AM
Handyhiker1 Handyhiker1 is offline
Registered-I
 
Join Date: Jul 2014
Location: Akron, Ohio
Posts: 447
Thanks: 284
Thanked 220 Times in 108 Posts
Default Onan JB vs JC

I do not have a JB, but do have a JC. Just wonder how close these are to each other as far as controls and basic trouble shooting.
It seems like much of the discussion for the JB problems fit the JC as well. There just isn't as much talk about the JC. I assume that the reason is the JB is just a much more popular set and there are many more of these out there.
Is it the same basic set just with 2 more cylinders and a bigger gen end?

JB- 6.0
JB- 7.5

JC- 10.0
JC- 12.5
JC- 15.0

Seems like double the cylinders, double the output? Also double the fuel used. Just asking so I can learn more about my JC if I follow the JB threads. Nothing wrong now just trying to gain some knowledge.
Reply With Quote
Sponsored Links
  #2  
Old 08-13-2017, 08:43:35 AM
JohnnyC JohnnyC is offline
Subscriber
 
Join Date: Jun 2014
Location: Boonton, New Jersey
Posts: 3,655
Thanks: 979
Thanked 1,649 Times in 977 Posts
Default Re: Onan JB vs JC

I have/had both. Restored both nut to bolt. Still got the JB. Both great sets with nothing bad to say about either. To me, the JC is a "double" JB but with a distributor. Loved my ex 15.0 JC, but too heavy to roll around. I need to have portable gensets here. Output somewhat doubled depending if your talking about the variation of JB and JC and options such as extended stack (B150 option) and voltage. Many parts shared between the JC and JB. Can't kill either except if the set is a victim of a nuclear blast.

Maybe there is a lot of JB activity at this time since it seems like these sets have been appearing frequently for sale and bought by members this year and those that already had JBs are jumping in to help. I bought my JB in late December 2016. Earlier in the year I was looking high and low for a JB in my immediate area with none to be found. Now they are coming out of the woodwork. Can't wait for this to happen to the Kubota gensets....

JohnnyC
New Jersey
Reply With Quote
The Following 2 Users Say Thank You to JohnnyC For This Post:
  #3  
Old 08-13-2017, 10:14:35 AM
Jim McIntyre's Avatar
Jim McIntyre Jim McIntyre is offline
Subscriber
 
Join Date: Nov 2004
Location: Mooresville, Indiana, USA
Posts: 3,787
Thanks: 612
Thanked 1,986 Times in 1,169 Posts
Default Re: Onan JB vs JC

Yes - same controls, same regulator (YD anyway), same basic engine, same heads, same starter, same carb, same fuel pump, same crankshaft... Oh wait... NOT same cranshaft

JB has two more cylinders, twice the output, and twice the fuel consumption...

Of course there was the 3-cylinder J3 variant, but they're a little harder to find. Much like the Onan CCK-AF model was.
Reply With Quote
  #4  
Old 08-13-2017, 10:24:45 AM
Onan Dan's Avatar
Onan Dan Onan Dan is offline
Subscriber
 
Join Date: Oct 2012
Location: Waynesburg, Pennsylvania
Posts: 3,548
Thanks: 7,760
Thanked 2,569 Times in 1,319 Posts
Default Re: Onan JB vs JC

Weight jb 7.5 like 425 pounds and the jc 12.5 like 750 pounds
Reply With Quote
  #5  
Old 08-13-2017, 11:20:37 AM
Billy J Shafer's Avatar
Billy J Shafer Billy J Shafer is offline
Subscriber
 
Join Date: Nov 2004
Location: Centerville, Texas
Posts: 15,991
Thanks: 8,146
Thanked 13,270 Times in 6,248 Posts
Default Re: Onan JB vs JC

Quote:
Originally Posted by Jim McIntyre View Post
Yes - same controls, same regulator (YD anyway), same basic engine, same heads, same starter, same carb, same fuel pump, same crankshaft... Oh wait... NOT same cranshaft

JB has two more cylinders, twice the output, and twice the fuel consumption...

Of course there was the 3-cylinder J3 variant, but they're a little harder to find. Much like the Onan CCK-AF model was.
Never seen a three cylinder J. But I had never seen a one cylinder J. Until I ran into the MJA.
__________________
I don't talk to myself. This early in the morning. Why the hell should I talk to you.
Reply With Quote
  #6  
Old 08-13-2017, 01:32:23 PM
len k len k is online now
Registered-III
 
Join Date: Jun 2012
Location: Manchester, New Hampshire
Posts: 13,878
Thanks: 362
Thanked 5,008 Times in 3,644 Posts
Default Re: Onan JB vs JC

Yes double the size double the fuel consumption
7 JB no-load ~ .6 gal/hr gasoline, full-load ~ 1.2
15 JB no-load ~ 1 , full-load ~ 2.4

a 12.5 JC is same engine as 15jc , but genhead just can't take as many amp, so no=load fuel consumption is same as 15jc , full-load is ratioed at ~ (12.5/15) *2.4 gal/hr

So good to not have bigger gen than you need or fuel consumption over cumulative hours ( few weeks total ) can add up $$$

For diesel cut everything in 1/2 approximately.
Reply With Quote
  #7  
Old 08-14-2017, 07:20:37 AM
Max Thompson Max Thompson is offline
Sponsor
 
Join Date: May 2009
Location: N.W. Missouri, USA
Posts: 5,665
Thanks: 4,880
Thanked 5,182 Times in 2,844 Posts
Default Re: Onan JB vs JC

[QUOTE=Handyhiker1;1409936]
It seems like much of the discussion for the JB problems fit the JC as well. There just isn't as much talk about the JC. I assume that the reason is the JB is just a much more popular set and there are many more of these out there.
Is it the same basic set just with 2 more cylinders and a bigger gen end?/QUOTE]

The only major difference in controls is the JB has a twin tower coil with no distributor.The JC has a automotive type distributor with the points located inside, the JBs points are located within the centrifugal switch assy.

More discussion on the JBs because they are just kind of junky old sets and the JCs are top of the line Onans.

That statement should stir the pot for at least a day or 2. (Love ya Leon)
Reply With Quote
The Following 6 Users Say Thank You to Max Thompson For This Post:
  #8  
Old 08-14-2017, 08:39:29 AM
BRae's Avatar
BRae BRae is offline
Sponsor
 
Join Date: Oct 2013
Location: Escanaba, Michigan
Posts: 625
Thanks: 267
Thanked 350 Times in 201 Posts
Default Re: Onan JB vs JC

QUOTE]

More discussion on the JBs because they are just kind of junky old sets and the JCs are top of the line Onans. QUOTE]

Uh Oh! The now.
Reply With Quote
The Following 4 Users Say Thank You to BRae For This Post:
  #9  
Old 08-14-2017, 09:26:40 AM
grif grif is offline
Registered-III
 
Join Date: Oct 2011
Location: Yakima, Washington
Posts: 1,210
Thanks: 396
Thanked 312 Times in 229 Posts
Default Re: Onan JB vs JC

Quote:
Originally Posted by BRae View Post
QUOTE]

More discussion on the JBs because they are just kind of junky old sets and the JCs are top of the line Onans. QUOTE]

Uh Oh! The now.
Methinks Max is bored and needed something to get him moving ;-)
Reply With Quote
The Following User Says Thank You to grif For This Post:
  #10  
Old 08-14-2017, 09:29:35 AM
Leon N. Leon N. is offline
Registered-III
 
Join Date: Oct 2009
Location: N. Chelmsford, MA, USA
Posts: 3,227
Thanks: 594
Thanked 1,867 Times in 1,110 Posts
Default Re: Onan JB vs JC

You guys should remain as trouble solvers and not trouble makers. Just kidding of course. You should not disparage the JBs. What's junky is the stuff produced today. From a strictly mechanical viewpoint, I would prefer the JC over the JB simply because of the ignition system design. On the other hand, The JB ignition system has fewer parts but at the same time it can bite the uninitiated if not careful.

I can hardly wait to tear into my JB to find out why it is so lazy picking up a load. Got my comp gage now, going after a timing light next. Hate to spend the $ but can't wait to see if that mechanical advance is stuck. First got to get the relatives on there way and keep an eye on the weather.
Reply With Quote
The Following 8 Users Say Thank You to Leon N. For This Post:
  #11  
Old 08-14-2017, 10:51:29 AM
len k len k is online now
Registered-III
 
Join Date: Jun 2012
Location: Manchester, New Hampshire
Posts: 13,878
Thanks: 362
Thanked 5,008 Times in 3,644 Posts
Default Re: Onan JB vs JC

JB vs JC may be a regional thing. Here in the north A/C cooling is not a necessity and most homes are heated with oil or nat gas so 7.7kw JB is plenty to run essential loads of most of the houses.

Down south I hear it's so hot central A/C cooling is a necessity so may need the higher power of a 15 kw JC. All depends on how big your A/C is.

Other thing is JC weighs almost twice a JB, ~ 800# VS ~475, so can't really say a JC is portable to roll out of your garge

Last edited by len k; 08-14-2017 at 11:09:32 AM.
Reply With Quote
  #12  
Old 08-14-2017, 11:20:17 AM
Wayne 440 Wayne 440 is offline
Registered-III
 
Join Date: Nov 2004
Location: Kentucky
Posts: 4,893
Thanks: 291
Thanked 3,974 Times in 1,896 Posts
Default Re: Onan JB vs JC

Quote:
Originally Posted by len k View Post
... portable to roll out of your garge
Not a JC, but "portable" is often determined by what you have to roll it with...
Attached Thumbnails
Click image for larger version

Name:	portable set.jpg
Views:	37
Size:	95.3 KB
ID:	288576  
Reply With Quote
The Following 2 Users Say Thank You to Wayne 440 For This Post:
  #13  
Old 08-14-2017, 11:39:58 AM
len k len k is online now
Registered-III
 
Join Date: Jun 2012
Location: Manchester, New Hampshire
Posts: 13,878
Thanks: 362
Thanked 5,008 Times in 3,644 Posts
Default Re: Onan JB vs JC

My JB is still sitting on the boat trailer I picked it up with. Got to find a place to put it....and way to lift it off.
.

Last edited by len k; 08-14-2017 at 12:23:23 PM.
Reply With Quote
The Following User Says Thank You to len k For This Post:
  #14  
Old 08-14-2017, 04:31:46 PM
PopsGarage PopsGarage is offline
Subscriber
 
Join Date: Dec 2013
Location: Barnegat, New Jersey
Posts: 522
Thanks: 129
Thanked 246 Times in 190 Posts
Default Re: Onan JB vs JC

Len It looks like it is easier to work on wile it is on the trailer..

Bob
Reply With Quote
  #15  
Old 08-14-2017, 04:46:35 PM
len k len k is online now
Registered-III
 
Join Date: Jun 2012
Location: Manchester, New Hampshire
Posts: 13,878
Thanks: 362
Thanked 5,008 Times in 3,644 Posts
Default Re: Onan JB vs JC

Yes, it is much easier. I do like it raised up since I have old knees, but that creates an issue of I don't want a tall doghouse for it.....yard cosmetics. Thinking of a shed like Leon's, I'ld want it far corner of the lot. But want to be able to drive a car up to it and tap car's 20 gal gas tank so don't have to carry that heavy gas. Got to replace backup car's in tank gas pump, so maybe I'll add a tank tap while I have tank open.
Reply With Quote
  #16  
Old 08-14-2017, 07:00:55 PM
Handyhiker1 Handyhiker1 is offline
Registered-I
 
Join Date: Jul 2014
Location: Akron, Ohio
Posts: 447
Thanks: 284
Thanked 220 Times in 108 Posts
Default Re: Onan JB vs JC

Quote:
Originally Posted by len k View Post
My JB is still sitting on the boat trailer I picked it up with. Got to find a place to put it....and way to lift it off.
I tottaly understand this. The Witte dieselelectric generator I got this spring is also still on the trailer. Never thought about how to unload it till I got home. The big problem is it weighs about 2500#. I am trying to barrow a fork lift but we will see what happens.
Reply With Quote
  #17  
Old 08-14-2017, 07:04:11 PM
len k len k is online now
Registered-III
 
Join Date: Jun 2012
Location: Manchester, New Hampshire
Posts: 13,878
Thanks: 362
Thanked 5,008 Times in 3,644 Posts
Default Re: Onan JB vs JC

My issue is more about I haven't thought thru where I want to put it.

To lift it can always find one of those huff-loader snow plow guys and give him some beer money.
Reply With Quote
  #18  
Old 08-14-2017, 07:13:45 PM
Handyhiker1 Handyhiker1 is offline
Registered-I
 
Join Date: Jul 2014
Location: Akron, Ohio
Posts: 447
Thanks: 284
Thanked 220 Times in 108 Posts
Default Re: Onan JB vs JC

I went to HF and bought the cheaper engine hoist they have. Had a 20% off coupon for it, cost was $120ish if I remember right. Even being the smaller one they sell, it picks up the JC easy and lets me roll it around. That is how I set the cck in the trailer too.
Reply With Quote
  #19  
Old 08-14-2017, 07:57:28 PM
JohnnyC JohnnyC is offline
Subscriber
 
Join Date: Jun 2014
Location: Boonton, New Jersey
Posts: 3,655
Thanks: 979
Thanked 1,649 Times in 977 Posts
Default Re: Onan JB vs JC

Quote:
Originally Posted by len k View Post
My JB is still sitting on the boat trailer I picked it up with. Got to find a place to put it....and way to lift it off.
.
Len, your JB needs a JohnnyC paint job

JohnnyC
New Jersey
Reply With Quote
  #20  
Old 08-14-2017, 08:15:50 PM
Handyhiker1 Handyhiker1 is offline
Registered-I
 
Join Date: Jul 2014
Location: Akron, Ohio
Posts: 447
Thanks: 284
Thanked 220 Times in 108 Posts
Default Re: Onan JB vs JC

And a different oil filter!!
Reply With Quote
The Following User Says Thank You to Handyhiker1 For This Post:
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

F o r u m Jump


Use "Ctrl" mouse wheel to change screen size.
All times are GMT -4. The time now is 01:54:35 PM.

Smokstak and Enginads site search!


All use is subject to our TERMS OF SERVICE
SMOKSTAK® is a Registered Trade Mark - A Community of Antique Engine Enthusiasts
Copyright © 2000 - 2016 by Harry Matthews P.O. Box 5612 - Sarasota, FL 34277