Carb butterfly barely open and high RPMs

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Trav300
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Carb butterfly barely open and high RPMs

Postby Trav300 » Mon Jun 29, 2020 9:56 am

Hello, I got my first cub last week. It would not start at all. It needed points, timing, fuel tank cleaning, fluids, and carb cleaning and now it idles nice and smooth. My issue is that if i move the throttle up 2 notches from idle the engine rpms are screaming! The same thing also happens if I move the gov to carb linkage the smallest amount (like and 1/8 of an inch). Adjusting the max rpm screw on the governor makes no difference. The butterfly in the carb is connected and everything seems to look good...Any ideas what could be causing this? Its like its pulling to much air/fuel

Thanks
Travis

Eugene
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Re: Carb butterfly barely open and high RPMs

Postby Eugene » Mon Jun 29, 2020 10:12 am

Welcome.

First thing to check is to see if the throttle and choke linkage are properly connected. The are easily reversed on the back side of the carburetor and the carburetor will react as described. To check, pull choke lever and see if the choke lever on the outside of the carburetor moves as it should.

Another common problem area. The throttle lever clamp on the side of the carburetor is slipping.

More things to check, easy stuff first.
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outdoors4evr
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Re: Carb butterfly barely open and high RPMs

Postby outdoors4evr » Tue Jun 30, 2020 6:25 am

Do these checks with the engine off!
The throttle control rod that goes from the governor to the carburetor should actuate as follows:
Push rod forward toward front of tractor = closes butterfly (Idle Down or Reduce RPM's)
Push rod back toward back of tractor = Opens butterfly (Idle Up or Increase RPM's)

Perhaps someone put the throttle actuator on the carb upside down.
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Gary Dotson
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Re: Carb butterfly barely open and high RPMs

Postby Gary Dotson » Tue Jun 30, 2020 7:05 am

First off, the linkage checks referred to above, then lube all linkage pivot points and made certain that everything moves freely and smoothly. Next step is to check adjustment of the governor rock shaft to carburetor linkage. The basic process is: engine off, remove the pin coupling the linkage rod to the rockshaft arm, advance the throttle lever to at least half throttle, hold the carburetor throttle lever in the wide open position, adjust the clevis on the linkage rod to where to pin will just slide back in snugly. This is the basic governor staging adjustment, not intended as a tuning adjustment. While doing this, you may encounter some slop in the rockshaft lever, if so, hold it lightly in the forward side of the slop. After doing this, if it still revs wildly with only small throttle advances, you may have a problem inside the governor, it's rare but not unheard of.

Trav300
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Re: Carb butterfly barely open and high RPMs

Postby Trav300 » Tue Jun 30, 2020 7:12 am

Thanks for the information guys. Ill go through all the linkages thoroughly. I think I may also have found the culprit or at least an issue. There is a pin in the governor that connects the 'cradle' that holds the weights to the shaft. That pin had come out and was laying in the bottom of the gov. housing. So I believe the weights were not spinning when the tractor was running. Basically the shaft was turning but the weights were not. I need a gasket before putting it back together and giving it a shot.

Thanks,

Gary Dotson
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47 Leader "B" (Herckie)
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49 Leader "D" very rough
48 Leader "D" unrestored
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Re: Carb butterfly barely open and high RPMs

Postby Gary Dotson » Tue Jun 30, 2020 8:57 am

Well, that would certainly do it! Here on the forum, the governor is often blamed for other problems. The governor is probably the least understood of all systems on the tractor. Also, if you found the slop I mentioned earlier, there are posts in the how to forum, showing a couple ways to easily tighten it up.

Trav300
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Massey Ferguson 241
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John Deere 110TLB

Re: Carb butterfly barely open and high RPMs

Postby Trav300 » Mon Jul 06, 2020 8:56 am

I reconnected the gov and it immediately fixed the problem. Difficult to get the pin back in though...

Thanks for all the responses.

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Re: Carb butterfly barely open and high RPMs

Postby k hutchins » Mon Jul 06, 2020 8:48 pm

That same exact thing happened to me years ago.
It's what introduced me to this forum, looking for an answer. Rudi and Bigdog came to my rescue in those days.
When l read your original post that's where my mind automatically went. Before l could answer, you had fixed the problem :{_}:
Good for you and well done

By the way welcome to the best place for troubleshooting Cubs and getting help.
Why is there never enough time to do the job right, but always enough time to do it over. :?:


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