Another 8n governor/carb problem

[XterraJohn]

I have a '48 8n and just rebuilt the carburetor. It runs beautifully, EXCEPT, once you increase the RPMs using the hand throttle, when you lower the throttle, the engine does not return to an idle. With nothing connected to the carburetor and the engine off, the throttle moves very easily with no binding.

With the engine off and everything connected, everything appears to work properly, with the throttle returning all the way to the idle-stop whenever the hand-throttle is moved to the idle position. However, once the engine is running, moving the hand-throttle to the idle position moves the governor to the idle position, but the throttle on the carburetor is staying open slightly, causing the spring-loaded connectors on the end of the throttle rod to stretch. Once the engine is turned off, you can see the throttle lever snap closed back to the idle-stop position.

It's almost as if the engine vacuum is causing the throttle butterfly to stick open.

What am I missing here?

 

[Soundguy]

is there any preload on the governor springs?

any binding ? ( if you use a finger to nudge the gov to carb rod?

if you manually goose the throttle rod does the gov fight you?

is the gov to carb rod to short ( bent)?

soundguy

 

[XterraJohn]

is there any preload on the governor springs?

any binding ? ( if you use a finger to nudge the gov to carb rod?

if you manually goose the throttle rod does the gov fight you?

is the gov to carb rod to short ( bent)?

soundguy

Thanks for the reply.

The governor appears to be functioning correctly, but, when it tries to pull the throttle to idle, instead of the throttle moving to the idle position, it just stretches the springs in the ends of the control rod. The weird part is that the throttle snaps shut as soon as you turn the ignition off.

I'm not sure exactly which spring you're talking about when you refer to preload. If you mean the big spring between the two rods on the outside of the governor, then, I don't have that information right now, but I can try to check in the coming days.

I couldn't find any binding at all, and if I try to manually goose the throttle, the governor fights back.

The rod is, in fact, bent. I was actually able to make the problem better by bending the rod more. This way, when the governor tries to pull the throttle shut, the springs in the rod stretch, but it's short enough that it still pulls the throttle closed. However, I don't feel that this is the "correct" way to fix the issue, and, if possible, I want to fix it the right way.

Is it possible that the springs in the control rod have just gotten too weak, are are stretching when they're not supposed to?


As an aside, I took the governor off the tractor because it was leaking oil and occasionally making a terrible rattling noise. It appears that someone has rebuilt the governor at some point in the past, as there was a good layer of silicon all around the gasket. The bearing and races appear to be in great condition. However, apparently, they didn't put in the correct number of shims, and the bearings were allowed to contact the housing, and have worn a spectacular groove in it, at one place even allowing oil to slowly seep through the housing. I have some more shims on order have tried to patch the cracks in the groove with a good coating of JB Weld, but at any rate, I'm afraid that I won't be able to do too much troubleshooting until I get it all back on the tractor.

 

[Soundguy]

Maybee you should start by getting a manual since you don't feel it's correct to bend the rod to adjust the length... guess what.. that's what the manual says to do! remember you are working on 30-50's era technology here...

yes on the spring tension / preload.

soundguy

 

[simonmeridew]

Hi John
The parts to repair / rebuild the governor are readily available. I did some rather crude shade-tree type rebuilding on my 8 N governor some 30 years ago and it's been fine since. The governor is a remarkable piece of machinery that operates quietly, and flawlessly behind the scenes once you get it set up right.

You can order what you need from just 8Ns in S. Carolina.

http://just8ns.com/index1.htm

is the website. Quick delivery

simonmeridew

 

[XterraJohn]

Thanks for the tip. After tearing into it, the problem appeared to be that someone before me had attempted to rebuild the governor and had not put the proper number of shims on the governor shaft. This was allowing the bearing race to expand too far and letting the governor balls contact the housing as they spun around. It really chewed up the housing, causing small fractures that were letting oil seep through the side of the casing. I coated the affected part with JB Weld and reassembled the governor today with additional shim and it appears to work much more quietly now.

For all intents and practical purposes the governor and carb linkage works well enough, but I still am a little confused as to why I had to bend the connecting rod so much in order to get the engine to idle. (It's probably bent at about a 45-degree angle.) I find it very odd that the governor can pull the throttle to idle with the engine off, but apparently is unable to do so with the engine running. For whatever reason, with the engine running, more force seems to be required to bring the throttle closed. This only appeared after I rebuilt and readdjusted the carburetor.

Hi John
The parts to repair / rebuild the governor are readily available. I did some rather crude shade-tree type rebuilding on my 8 N governor some 30 years ago and it's been fine since. The governor is a remarkable piece of machinery that operates quietly, and flawlessly behind the scenes once you get it set up right.

You can order what you need from just 8Ns in S. Carolina.

http://just8ns.com/index1.htm

is the website. Quick delivery

simonmeridew

 

[Soundguy]

it's just the nature of the machine.. go ahead and get that manual..

soundguy

 

[XterraJohn]

I fired the tractor up today and tried to more thoroughly adjust everything. What I found was, if I bent the rod enough to get the carb down to idle, it wasn't long enough to allow full-throttle. If I straightened it enough for full-throttle, it wouldn't pull the carb down to idle. There seemed to just be too much play in the spring connectors on the end of the rod.

So......I tack-welded one of the connectors to the rod so it would stop flexing. At this point, it seems to work perfectly. :thumbsup:

 

[Soundguy]

yep.. they don't last forever. You can get new repops, or better salvage ones if needed, as now that they are welded ya can't remove them

soundguy

 

[XterraJohn]

Yeah, I considered ease of removal before going this route. I only welded one end so that if either the carb or the governor needs to be removed, it can still be done. However, if the governor comes off, the rod is most likely going to have to come with it unless we cut it off with a rotary tool or something.

For reference, here's a picture: