Throttle Not Opening All the Way Up

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Throttle Not Opening All the Way Up

Postby DieselDennis » Fri Jul 05, 2013 10:16 pm

Fresh off getting the '48 running again, we've run into a little snag in helping her reach full potential.

The governor seems to not let the engine go all the way to wide open throttle. Since there is no tach, it's kind of hard to tell what it's leaving on the table. I know that there is no change in engine RPM over the last three notches of the throttle. I can physically go push the rod between the governor and the carb back and it will run faster, but the rod is constantly fighting against me to go back away from the carb.

Tractor is running good otherwise for the most part. Was going to do a little clipping today with the C-2, but with the engine not getting to full throttle, those plans were stalled.

Anyone know of some things to check with the governor? I never opened it up. Didn't want to mess with it because I really didn't want to get into it if it ran OK. Can I unstick the weights from the outside? Is there any oil in it? I see a small drain plug in the front. Think if I flushed it with some diesel it would free up? Any other ideas that don't involve taking off the hood & fan?

Here's to some seat time tomorrow for everyone !
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Re: Throttle Not Opening All the Way Up

Postby Barnyard » Fri Jul 05, 2013 10:28 pm

Dennis, go to this web page http://www.cleancomputes.com/Cub/Blue%2 ... System.htm and go to the bottom of page 28 "Sychronizing the governor to carb throttle movement.
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Re: Throttle Not Opening All the Way Up

Postby Rudi » Fri Jul 05, 2013 10:34 pm

Dennis:

Many times it isn't the governor itself but the linkages that may be binding up a bit. Suggest you spray a good penetrating oil into all the connections on the linkage as well as the bumper spring, let them soak a bit, spray some more and try to move the governor rod a few times each spritz to help clean out and lube the connections. With luck that is all that needs to be done. See the drawing below:

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Re: Throttle Not Opening All the Way Up

Postby DieselDennis » Fri Jul 05, 2013 10:54 pm

Rudi & Barnyard, Thanks for the tips.

I had sprayed all the linkages a few times hoping to "free it up" and forego an invasive operation. I considered adjusting the control rod to the carb today, but didn't figure that was the real problem. Rust tells me it's been like that for a while. Ofcourse thanks to Barn's link I see now that lengthening the rod is a technical procedure called synchronizing. Maybe tomorrow I can also look real close and see if it's hitting the maximum speed adjusting top screw.

And to add flavor to the discussion, this '48 has a Zenith carb. So who knows if things were sync'd upon installation.
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Re: Throttle Not Opening All the Way Up

Postby gitractorman » Sat Jul 06, 2013 4:07 am

Also double check that the rod from the governor arm to the carburetor is not rubbing on the engine block. I've ran across more than one cub where this was the case, and you just could not see that it was hitting. It doesn't take much of a touch to that rod to keep it from moving fully. Years of re-painting, oil, grease, dirt, rust, etc, can easily build up there and cause it to rub and not let the governor actuate the carb butterfly fully. Trust me, it's worth looking closer at before you do anything else.
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Re: Throttle Not Opening All the Way Up

Postby RaymondDurban » Sat Jul 06, 2013 5:24 am

After you have checked the stuff the guys mentioned, check item 13 in the pic above. It is the max allowable RPM set screw. If item 11 is pulled all the way till it contacts 13, the engine won't rev any higher with the throttle lever. Then check the spring itself (7). Look for uneven pull on the spring with the throttle set to high. With age, the spring gets weak and can no longer over power the weights inside the governor, which won't allow full high RPMs.
With both of these, you'll still be able to manipulate it with the rod on the left side to get higher settings, but not the lever will have no affect.
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Re: Throttle Not Opening All the Way Up

Postby Scrivet » Sat Jul 06, 2013 7:28 am

DieselDennis wrote: .....The governor seems to not let the engine go all the way to wide open throttle. Since there is no tach, it's kind of hard to tell what it's leaving on the table. I know that there is no change in engine RPM over the last three notches of the throttle. I can physically go push the rod between the governor and the carb back and it will run faster, but the rod is constantly fighting against me to go back away from the carb.
.......
I'm going to take a little different approach than the others in my advice. While you may have a calibrated ear and intuition to let you know it's not getting to 1800 RPM, I would get (buy or borrow) a hand held tach and stick it on the PTO or an electronic one clipped to the coil and KNOW FOR SURE. Then follow the suggestions given including synchronizing the carb BEFORE monkeying with the governer internals. It could be something drastic broken but I'll bet it's just a little wear and a small adjustment off.
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Re: Throttle Not Opening All the Way Up

Postby Lurker Carl » Sat Jul 06, 2013 8:13 am

I don't understand why you didn't take the tractor out to mow unless the Cub did not have enough power to spin up the mower. You should not see wide open throttle when the tractor is stationary and the engine has little to no load. That would indicate a tune up or mechanical repairs are imminent.

Plowing or mowing are a different story, low power may be traced back to wide open throttle never occuring. There may be enough play (wear) in the joints between the governor and the carburetor to prevent the throttle plate from fully opening - wear at #6 key and in the two associated keyways is a major culprit for considerable play an unexpected location.
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Re: Throttle Not Opening All the Way Up

Postby John *.?-!.* cub owner » Sat Jul 06, 2013 8:45 am

I am going to go out on a limb and guess you are not used to working on engines with governors. The hand lever does not normally open the throttle plate all the way when running, unless there is a heavy load applied to the engine, then it attempts to bring it up to the 1800 rpm it is supposed to max at. There is a stop (small cap screw with jam nut) on top of the governor that limits maximum rpm, but before adjusting that you need to check the rpm, over speeding will shorten the engine life,as well as cause excessive vibration in mowers, or other pto driven attachments.
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Re: Throttle Not Opening All the Way Up

Postby DieselDennis » Sun Jul 07, 2013 7:56 pm

Carl & John,

You're right, I'm not used to dealing with governors at all. This tractor is more than twice as old as I am.

How can I know for sure that the governor is working correctly? I can try to go mow. Should I just ease into some thick grass and see if the governor will open the engine up more by itself?

One thing I would like to point out is that when I go and push on the rod to the carburetor, I am getting some resistance. I can push the rod in for maybe a couple of seconds and then the resistance comes. It gets stronger and eventually I have to push against it very hard to hold it. This makes me thing that I am pushing against the weights, as I think the spring resistance would be more linear.

Why do they have the last three notches on the throttle? Is this just the setting that the governor can open the engine up to should it have the need?

I am a little leery of opening up the governor. I'm also leery of adjusting the max RPM screw as I have no current way to check it.
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Re: Throttle Not Opening All the Way Up

Postby Lurker Carl » Sun Jul 07, 2013 8:10 pm

The resistance you feel is the governor saying, "Close the throttle! The engine is over speeding."

Take the tractor out and mow in second gear. The engine should run at a fairly steady speed, it may bog down or stall if you have very tall or thick vegetation to mow. If it does, shift to first gear or take a "half bite" with each pass. There should not be any surge or lag as the load changes. The governor is a cruise control that keeps the engine at peak torque.
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Re: Throttle Not Opening All the Way Up

Postby Bill Hudson » Sun Jul 07, 2013 8:15 pm

Diesel,

Here is what you need to check your RPMs. http://www.ebay.com/itm/VINTAGE-STEWART-WARNER-SW-Hand-Held-TACHOMETER-TACH-METER-0-4000-RPM-R-/380671518293?pt=LH_DefaultDomain_0&hash=item58a1ca6655 Lots of folks use these to check RPMs, they are not all that expensive and accurate enough for working on our Cubs.

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Re: Throttle Not Opening All the Way Up

Postby John *.?-!.* cub owner » Sun Jul 07, 2013 8:41 pm

try just driving it up a hill in 3rd gear.
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Re: Throttle Not Opening All the Way Up

Postby Rudi » Sun Jul 07, 2013 10:17 pm

Dennis:

I have two of these and they are really handy to have. Pretty darn accurate .. they are a must in my tool box :!:

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Re: Throttle Not Opening All the Way Up

Postby Rick Spivey » Mon Jul 08, 2013 5:14 am

I doubt any cub that is functioning correctly actually uses all the notches up, and has a noticeable increase in engine speed at each new both setting. Some of them only use 1/2 the notches to achieve full throttle settings. I wouldn't worry about the last three notches, nor the fact that you can move the throttle lever when at "full throttle" setting. Both are normal. As others have said, focus on the correct things here, which are removing any slop in the governor to carburetor linkage, and the actual RPM measured at "full throttle" setting on your throttle quadrant.
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