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Discussion Starter · #1 ·
My 646 has an onan that didn't come in a case... I don't have my notes but I think it's a NHC from a generator, welder or something. The carb is a zenith.

I had the throttle cable hooked directly to the carb when I bought it (governor was bypassed) and I'd like to make the governor work as it should.

I took the carb off and gave it a good soak/cleaning and here's what I have now (not bolted on but showing how it was hooked up.


And here's what's under the carb (governor lever on the left)


My plans:
Take off the screwy way that the throttle was attached before (the yellow piece between the governor link and the carb.
Hook the governor link directly to the carb as I believe it was in the first place.
Fab a bracket that allows me to move the throttle cable to the far side (right side looking from the seat.
Fab an arm that mounts to the governor linkage that allows me to adjust the throttle from the right by supplementing the fixed spring or by working against it.

Does this sound like a reasonable approach?
At the moment the springs on the governor arm forces the throttle wide open when the engine is not running... is this correct?

Any advice would be appreciated.

I'm going to to run the throttle cable on
 

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Your question has been duly noted. Perhaps the person best qualified to advise you is Boomer. You can either wait for him to see your thread or you can click on the MEMBERS link at the top right half of this page. Click on Boomer's name and then look for the link on the left side to send him an e-mail.

Or you can go to the FAQ's section, find the "Where to buy STUFF" document and look for Boomer's contact info under the Onan parts section. Just pick up the phone and call him.
 

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Discussion Starter · #4 ·
Boomer.... Thanks for the response. I look forward to hearing your feedback. I didn't want to contact you directly but I was hoping that you would jump in on this thread.

As an experiment I took off the plate that was bolted to the carb that was between the governor link and the throttle butterfly connection. It's mostly yellow in the picture. One of the 'Bolts' that was holding it on was a round headed pivot bolt and I put that back in the same hole when I re-assembled.

At rest with the engine off the throttle is pulled wide open. I started it and pretty much as soon as the engine fires up the governor pulls the throttle to closed (up against the stop screw)... I'm guessing this means that the internal parts of the governor aren't totally hosed. Perhaps (it's likely) that I have the wrong spring or lever on the governor?

I read enough about onan governors yesterday to get confused but I'm pretty sure that when the engine is running that it should not be against the stop screw if it's set up properly.... I'm not surprised that I am not set up properly just yet.

So for the time being (again, I know it's not ideal) I adjusted the stop screw a bit to bring the RPMs up to where they should be. Both the choke and throttle cables are disconnected. The good part is that the governor now has a chance to do something unlike the way it was set up when I got it... The throttle cable overrode the governor by holding the throttle plate in place.

It starts and runs OK now so that's good. If I grab the governor and pull it to open the throttle the engine doesn't rev up smoothly, it does that bwuuuh hollow sound that you tend to get when things are out of adjustment. Not sure if that's related to the governor or more to the fact that I just had the carb apart and I don't have the adjustments down correctly. Can anyone provide some advice on how to adjust the carb (again, it's a zenith)?

I can use the tractor as it is right now but I'd like to be able to have the throttle control hooked back up (the choke is a no brainer I think)

Thanks a bunch for the help on this.
 

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Onan Master, new and used parts.
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notelvis said:
Boomer.... Thanks for the response. I look forward to hearing your feedback. I didn't want to contact you directly but I was hoping that you would jump in on this thread.

As an experiment I took off the plate that was bolted to the carb that was between the governor link and the throttle butterfly connection. It's mostly yellow in the picture. One of the 'Bolts' that was holding it on was a round headed pivot bolt and I put that back in the same hole when I re-assembled.

At rest with the engine off the throttle is pulled wide open. I started it and pretty much as soon as the engine fires up the governor pulls the throttle to closed (up against the stop screw)... I'm guessing this means that the internal parts of the governor aren't totally hosed. Perhaps (it's likely) that I have the wrong spring or lever on the governor?

I read enough about onan governors yesterday to get confused but I'm pretty sure that when the engine is running that it should not be against the stop screw if it's set up properly.... I'm not surprised that I am not set up properly just yet.

So for the time being (again, I know it's not ideal) I adjusted the stop screw a bit to bring the RPMs up to where they should be. Both the choke and throttle cables are disconnected. The good part is that the governor now has a chance to do something unlike the way it was set up when I got it... The throttle cable overrode the governor by holding the throttle plate in place.

It starts and runs OK now so that's good. If I grab the governor and pull it to open the throttle the engine doesn't rev up smoothly, it does that bwuuuh hollow sound that you tend to get when things are out of adjustment. Not sure if that's related to the governor or more to the fact that I just had the carb apart and I don't have the adjustments down correctly. Can anyone provide some advice on how to adjust the carb (again, it's a zenith)?

I can use the tractor as it is right now but I'd like to be able to have the throttle control hooked back up (the choke is a no brainer I think)

Thanks a bunch for the help on this.



Pages from NHC parts manual Spec A-E

I currently do not have any of these parts in stock.

Thank you
Boomer
The used Onan Engine Parts Guy
 

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Discussion Starter · #7 ·
yep... the picture on the top of page 15 is exactly what I have.... Good sleuthing. Thank you. It looks like I have nearly everything in that pic.

My problem is that I want to change part #9 (the speed adjustment stud) to myself (a studly guy who adjusts engine speed by my own choice).

I don't need to tell you that the engine in the picture (as well as my engine) was purposed for a fixed speed application (generator I think)... My problem is that I want to vary the engine speed occasionally on the tractor.... like when I get off to throw stuff in the bucket it would be nice to be able to idle down... or when my wife is calling me it would be nice to spin it up a bit to drone her out.

At the moment since I have the throttle cable disconnected and the governor is running the show I'm at it's mercy. I want to regain control of the engine but still have the governor help me maintain the desired speed.... just like my case 446 does.

I'm assuming that this is possible and that I'll likely have to make a few parts... no problem there. I'm confident that I can make whatever I need. My issue is that I'm not sure what to build.

So let's say I bring the throttle cable to the right side (as viewed from the seat, the far side of the carb in my pictures). I can easily make a bracket there to hold the sheath of the cable in a fixed position. Now comes the tricky part.... When I push the throttle lever up, the core of the cable extends from the sheath in a pushing action. How do I get that pushing action to the governor?

Logic tells me that I can't just attach the cable to the arm (or an extended arm) because that would not allow the governor to do it's thing and adjust the carb butterfly as needed to maintain speed. The linkage needs to have some give to it. I expect that the answer will be some sort of new arm that will be moved by the cable core. This new arm will have to connect via a spring to the existing (or newly fabricated) governor arm. I'm having a hard time visualizing how to make this happen in the space provided.

If there is some easier way or my thinking is flawed please let me know.

At some point I'll likely just start building something and see what happens... It might be more obvious once the cable is mounted in the right spot.

On a separate but related topic: When I manually override the governor and push the throttle higher with my hand it doesn't rev up smoothly ("vroom") but rather it
makes a hollow throaty sound ("bwhhhhhhhhhhuuuuhh") is there a common cause for this?

Thanks to all with insight into this stuff.
 

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Onan Master, new and used parts.
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note
a little bad news.
most genset engines of this era had ten flyballs in the governor.
this allowed the to run at 1800 rpm.
the fix is to remove the flywheel and front cover.
then remove five flyballs, and reassemble
then it will run at 3600 rpm.
good luck boomer ( the used onan engine parts guy)
 

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Onan Master, new and used parts.
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note
if you could get your governor working it would not let you run much over 1800 rpm.
as to pulling the engine, that depends on application.

sometimes you can remove the mounting bolts and jack up the engine.
NOTE do not loose the 1/8 ball under the gov arm shaft.
also the small wire clip on the front of the cam pin.
thank you. boomer (the used onan engine parts guy)
 

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The springs you will need are 10 coils and 15 coils the one your photo has over 30. m&d has parts I checked.

Throttle cable pull lever that tension spring this tension of spring open throttle plate on carb. by pulling lever on Governor arm second spring pull throttle plate back to Idle. When first spring relaxed by Throttle cable. Once look at it for 4 housr it get simple lol.
 

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Discussion Starter · #13 ·
Thanks again for the info guys.

My only real experience with governors was removing them from go-carts and golf carts as a kid. I never had to mess with on on a case.

So my understanding of a governor is (correct me if I am wrong) to manipulate the throttle plate of the carb based on the rpm in an attempt to get a relatively constant speed. The governor has a target speed (on a case around 3600rpm) and if the engine is running slower than that the governor opens the plate, if the engine is running faster than that the gov shuts the throttle butterfly a little. Does that sound correct?

Boomer: You say that "if you could get your governor working it would not let you run much over 1800 rpm."... sounds right... If my governor always wants to close when I'm over the desired RPM but it snaps open as soon as I kill it can I assume it's working? If you are right that my engine is set up for 1800rpm (I expect that you are) it makes sense that my carb is running against the idle stop which I had to screw in to achieve 'case like' (3600) rpms. Sounds logical. Technically my governor "is working" but it's seeking a speed much lower that I would like to have so it's 'pulling down' all the time (unless I happen to bog down to 1800 when it relaxes a little.

Gator_rider2:
Thanks for the specs on the springs... Where did you get your information? If it's a manual here (or someplace else online) I would love to read it. You said M&D has the parts... who are M&D? I'm not sure that I follow your explanation but I'll reread it a few more times and the light bulb might come on.

So when I open the engine to remove half of it's balls (pausing to reflect on that statement) will I need gaskets or any other supplies? Worst case scenario is that I pop it open and cant put it back together for some reason. I looked at it last night for a bit... If I rip the front end of the tractor off I think I can do it with the engine mounted. I planned on changing the oil and doing a travel valve rebuild so that might be a good time to pull the cooler and tank too.

The previous owner installed the engine so I don't know for sure where it came from. He mentioned that it was a replacement engine from a generator. I think that he said the shaft was too long so he cut it down for the tractor.... I assume that it was a non-taperd shaft. Some of the things he told me turned out to not be true so this is questionable information too.
 

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You are correct. The governor is there to try and make the engine run at a target RPM. Most outdoor power equipment uses 3600 RPM as the target speed. However, in order to get longer life and quieter operation, 1800 RPM is another target speed.


As I understand it, you can change the target RPM by changing the type of governor used. I'm not an Onan Xpert by any means but memory tells me that different governors used varying numbers of balls in them for the different target speeds. Boomer and or robynj can explain about that.


My concern for you is this. Your tractor was designed for a 3600 RPM engine that is driving a 8.5 GPM pump. If your engine runs at half the target speed, then you are getting half the oil flow. That means your ground speed is half what it should be and your loader reaction times are also at 50 percent. Whether any of that matters to you or not is totally your own judgment call. Perhaps you are happy with the way your tractor operates and that's OK with me. I'm just letting you know what's possible.
 

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Discussion Starter · #15 ·
Thanks tom... the fact that I may be running at half speed is really good news. I'd love to have a little more speed from the drive system.

I expect that my idle screw hack has me well above 1800rpms but I'll take more if I can get it.
 

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Gator_rider2:
Thanks for the specs on the springs... Where did you get your information? If it's a manual here (or someplace else online) I would love to read it. You said M&D has the parts... who are M&D? I'm not sure that I follow your explanation but I'll reread it a few more times and the light bulb might come on.

(Boomer parts diagram item 8 springs give number coils)

Pages from NHC parts manual Spec A-E

I currently do not have any of these parts in stock.

Thank you
Boomer
The used Onan Engine Parts Guy

(Boomer posted he did not have parts you needed so Google for you and posted link was http://www.m-and-d.com/Onan_parts.html)

I understand what trying to do.
You'll need to get to good point with fix speed so can change to variable speed.

Your first post shows spring that's not fixed speed are variable speed its not Onan part.

It will be easy to go to Limited speed once get right spring on Governor and take half your balls out. (Limited speed run Idle and full speed 3600 rpm's)
 

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Discussion Starter · #17 ·
Got it all torn down last night.... sadly it turns out that there are 5 balls in this governor so there really was not a need to break it down... I did uncover a few things along the way so I will make the best of it.
 
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