Engine surging badly

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cub67
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Engine surging badly

Postby cub67 » Wed Jul 24, 2019 8:29 pm

Hi all, I just picked up my second cub a few days ago. A non running 55. After cleaning and setting the points, cleaning out the gas tank and carb and priming the oil pump she fired up for the first time in at least 5 years as I was told. Then after repairing a bad shift fork the cub was mobile! I spent the next day changing fluids and adjusting things. The engine runs really good and smooth and accelerated pretty good too. I made the governor to throttle linkage adjustment and noticed that the rock shaft extension had a lot of play in it so I took if off and shimmed it up. Made the adjustment per manual. Now it surges like crazy. I have tried to adjust the bumper screw, re set the linkage adjustment 3 times and read probably every thread here that contained engine surging. I am stumped. I drove it around yesterday for over an hour proud as could be but today I couldn't get it out of my building. If I grab the linkage the surging will stop until the rpm is increased then it starts again. If anyone has any idea what I could try I would appreciate it. I was going to pull the governor housing off tomorrow and see if something in there might be causing the problem???

TallCoolOne58
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Re: Engine surging badly

Postby TallCoolOne58 » Wed Jul 24, 2019 8:44 pm

I think pulling the governor housing might be a good plan, with an eye out for a bent or broken bumper spring.

Another thought, how's the governor spring?
Opportunity is missed by most people because it comes dressed in overalls and looks like work-Thomas Edison

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tmays
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Re: Engine surging badly

Postby tmays » Wed Jul 24, 2019 8:46 pm

I would suspect fuel flow problem first. Yeah I realize you may have cleaned it all, but I’d recheck before I pulled the governor.
Thomas

Eugene
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Re: Engine surging badly

Postby Eugene » Wed Jul 24, 2019 9:13 pm

tmays wrote:I would suspect fuel flow problem first. Yeah I realize you may have cleaned it all, but I’d recheck before I pulled the governor.
Agree. Check the fuel flow and clean the carburetor main jet.

Then double and triple check the ignition timing with a timing light.

Also adjust the valve tappet clearance and conduct compression tests.

Basically, I'm suggesting to make sure everything is in good order before you start tearing into things.
I have an excuse. CRS.

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Re: Engine surging badly

Postby Waif » Wed Jul 24, 2019 10:23 pm

I leave a piece of wire on each Cub to check the main jet.
Of course that has reduced/eliminated needing to use one often. So far....
But it's an easy check.

Carb could be choking/restricted from crud in a line ,or at the inlet screen if it has one.
Make sure your fuel tanks vent is working too.

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Re: Engine surging badly

Postby inairam » Thu Jul 25, 2019 5:55 am

It is almost never the governor itself. Check the fuel flow and jet as others suggested and adjust the linkage between the governor and the carb. Make sure the tips to the rods for the choke and the governor linkage connections to the carb are clean and lightly lubed so they do not bind.
When you only have 9 horsepower you need to know the names of all of the ponies!

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Re: Engine surging badly

Postby Dale Finch » Thu Jul 25, 2019 6:26 am

In your initial post you said you "shimmed up" the rockshaft extension because it had a lot of play. Are you sure it doesn't still have a problem there? Was the play located where the shaft enters the governor? If yes, there is a small woodruff key that can wear, and a quick fix many have done is to pull that shaft out, clean it up and reinstall it with a dab of JB WELD.
Just a thought.
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cub67
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Re: Engine surging badly

Postby cub67 » Thu Jul 25, 2019 7:08 am

Wow a lot of good things to look at here. Thank you everyone. I will pull the main jet and clean it again. On the governor shaft extension what I did was pull it out and wrapped a pc of an old pop can around it in a "c" shape to the woodruff key to get rid of the radial play. JB weld is probably a better idea. I pulled the bumper spring out. How long should the spring be sticking out of the bolt? Mine is maybe 1/4 to 5/16" of spring exposed. I'll report back in a while!

inairam
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Joined: Wed Jul 08, 2015 10:24 am
Zip Code: 19342
Tractors Owned: 1948 6v - Dozer
1949 with kub klipper belly mower. mag 6v - Mom
1950 with plow, 54 blade, mott mag 6v - Roxanne
1953 54 blade, c22, wood 42 6v
1957 6v - barn Queen
1965 lo-boy with c-3 mower 12 v - Loboy
1974 Horse II 12 v c-2
1975 with woods 42-6 12 v - Horse
1979 long strip 12 v stuck engine
130 with international 1000 loader 6 v
1969 140 with bush hog tow behind mower 12 v
Terramite T-6 4WD Backhoe Perkins diesel
Memberships: Rough and Tumble Engineers Historical Association;Chapter 8 IH Collectors; IH Collectors Worldwide
Circle of Safety: Y
Location: Glen Mills PA

Re: Engine surging badly

Postby inairam » Thu Jul 25, 2019 7:46 am

Also check for an air leak on the carb to manifold seal. Picture of a new spring http://www.tmtractor.com/new/gv/1006fp.htm but that is not causing the surging.
When you only have 9 horsepower you need to know the names of all of the ponies!

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Re: Engine surging badly

Postby yellercub » Thu Jul 25, 2019 7:52 am

I had that problem and here is what seemed to be the problem. The top of the carb. was warped, so after flatting it and setting the float and an adjustment to the linkage yoke (the yoke that links to the gov. arm) the problem went away for me. Hope this helps. Good luck.

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Re: Engine surging badly

Postby Flemmingth » Thu Jul 25, 2019 1:33 pm

If you take the governor apart, look out for this viewtopic.php?f=1&t=101027#p798500
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Waif
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Re: Engine surging badly

Postby Waif » Thu Jul 25, 2019 1:58 pm

IF carb was removed to clean ..Checking choke lever position at carb is a quick check too.

cub67
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Re: Engine surging badly

Postby cub67 » Mon Jul 29, 2019 7:03 am

Hey all, thank you for all of the responses. I was able to get it settled down by cleaning the main jet (again) and re adjusting the control rod properly. The cub is running pretty good and the governor is responsive to load so I think it is ok. That carb top is warped pretty bad as it is always wet but I can live with that for now. I'll read up on possible solutions for that!

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Don McCombs
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Re: Engine surging badly

Postby Don McCombs » Mon Jul 29, 2019 7:45 am

You should have been at The Tug this weekend. You could have gotten that warped top fixed.
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