51 Cub to rebuild or not to rebuild

[1cubnow]

Hello All! New to this forum but have poked around a bit and have found it to be a great resource so thanks for being part of it!

Last week I picked up a 51 Cub. I’ve had a little time to tinker around with it and address some immediate things like changing the oil, putting some fresh gas in it, cleaning the air cleaner, reaming the line that runs from the crankcase to the air cleaner, and changing the hydrolic fluid. I also added half a can of sea foam to both the crankcase oil and the gas.

When I got the Cub it probably had been sitting for years with little to no use. Today I ran it for a few hours on and off. I plowed with a 193 single plow. I noticed that I could only plow in 1st gear as the tractor would either stall or didn’t have enough power to continue on. This is my first go around so may have been plowing fairly deep. Either way, it worked in 1st and was getting good furrows turned over. My biggest issue is my oil pressure gauge reading just above the red after one or two passes with the plow. I’m concerned about this. The hotter the machine gets to more it seems to creep closer to the red and will start loosing power and stall during plowing. Coolant level is fine and oil level is good. I have some blow from what I can see coming from the dipstick breather but not significant. No real smoke either from the stack. I’m beginning to think there i May need to do an engine rebuild kit to bring it up to speed and power. Any thoughts? Thanks all! Pics attached.

[k hutchins]

How deep were your furrows? 4-6" is plenty, if you're going deeper than that, or plowing really fallow soil that hasn't been turned in many years, the going is going to be tougher for sure.
I wouldn't worry too much about your oil pressure needle. Mine sits just above the red all the time after the engine warms up. On start up it's mid range. Once it hits running temp it will drop down. What weight oil are you running?
Just my opinion but if it's not leaking or burning oil, l would hesitate to do a deep dive into the engine. If it's been sitting for years without running, plowing virgin ground is one of the toughest chores you could give it right out of the box.
When l was plowing with mine (haven't for years) and it started to bog, l'd change the pitch on the plow and let go a bit shallower in tough ground.
My opinion.

By the way welcome to the forum.
I'm sure others have more to say.
Good luck on what you decide.

[Bill Hudson]

It is hard to tell from your pics, but it appears to me that you are plowing too deep for the 193 plow. The 193 has a 12" bottom which means normal plowing depth is about 6". Also, the furrow slices of the last two furrows are standing on edge which can happen when plowing too deep and/or not taking a wide enough (<12") furrow.

The pic of the plow shows a rusted moldboard and share. If you did not remove most of the rust prior to plowing, the plow will certainly be harder to pull and will not do a nice of a job plowing as a shiny moldboard and share.

Hope this helps. Pics of the plow in operating position in the field would be helpful for further analysis.

Bill

[ricky racer]

I suggest a compression test, first dry then wet and report back with your readings.

[Glen]

Hi,
They usually recommend on here to do a compression test, it will help you know if the engine is ok, or wornout.
You need a compression test gauge, with a fitting that will fit the Cub spark plug holes, to do the test.
The Cub service manual says a Cub engine has 120 lbs of compression, that is probably for a new engine.
They work ok with some less, 90 lbs or above is ok.
Remove all spark plugs at the same time for the test.
Open the throttle fully when doing the test, so the engine can get air.

A good tune up is good to do to a Cub you just bought.
Ignition points, condenser, distributor cap, rotor, spark plugs, and maybe spark plug wires, if they are old, or damaged.
The points get old and burned from use, then the engine doesn't run good.
The ignition timing is important, it has to be set right, or the engine can have less power than it should.
I would check the timing as one of the 1st things, if the engine has low power.
The Cub service manual says use a timing light, like cars used in the past.

Since Cub is a 1951, I'm guessing it has a Battery Ignition unit, but it could have a magneto.
Below are pages showing a Battery Ignition unit, and the points, and setting the point gap.

http://farmallcub.com/rudi_cub/www.clea ... age-11.jpg

http://farmallcub.com/rudi_cub/www.clea ... age-12.jpg

TM Tractor, at the bottom of the page, has new points and condenser. NAPA has them too, the last time I checked.
To change them, you need a short screwdriver, with a sort of wide blade, and an 11/32 open end wrench, for the nut holding the end of the point spring.
I sit down next to the engine, on a lawn chair, and use a good light. You can put a large towel on the ground, to catch any screws that might drop.
Or you can file the points flat, if they aren't burned much. Wipe off all filings with a clean cloth.

Below is a page from the Cub service manual, showing the timing marks for the Cub engine. They are at the left front of the engine.
A 1951 Cub probably has 1 mark on the pulley, mark number 1 in the pic.
Align mark number 1 with the pointer, when the engine is running at slow idle speed, about 500 RPM.
Use only the pic and the description below it, they are talking about other things on the page.

http://www.farmallcub.info/manuals/gss- ... 001-43.jpg

Check the timing with the timing light after setting the timing, and see if the timing advances as you speed up the engine. If the timing advance in the distributor is stuck, it could make the engine have less power than it should.
That is only on the Battery Ignition unit.

The crankshaft bearings could be worn some, making it have low oil pressure.
If you are using thin oil, that could make it have lower pressure, as it gets hot.
Thicker oil might help some to keep the oil pressure higher.

[Greenthumbfarms]

Those little Cub engines are runners. I bought one that hadn't done any real work for several years, just ran a few times a year to keep the oil moving through the engine. I had a friend who restores tractors look at it, thinking the engine was tired and needed a rebuild...he changed the points, plugs, and rebuild the carb and the tractor runs like new. Says not to tear a cub apart unless it runs poorly all the time. A Carb rebuild and retuning can help.

Now if i could just get Russ to come back and put new gaskets in so the engine wont leak so much oil...

[1cubnow]

Thanks All for your help on this! Super informative. Yeah, I'm probably plowing around 6-9" deep without getting an exact measurement and the soil is fairly fallow as well. Probably too deep. I'm running SAE 30 oil in it now and noticed it went grey rather quickly after changing and running the tractor for the time I plowed. With your comments I'm now leaning more towards diagnostic measures rather than jumping into a rebuild. @Geln, thanks for all the detailed info as I really appreciate it. Gonna start with checking timing and yes my machine starts via a battery. 6v I believe. Gonna check compression as well but not sure what 'Wet vs Dry' means. Suggested to remove all plugs at the same time for test...I take it you attach the tester to each plug hole one at a time and crank the engine to get a reading on each cylinder, is that correct? Will check manuals as well. Thanks so much all!

[Don McCombs]

Adjust the plow, do some more plowing and give the Seafoam time to do it’s job. It doesn’t provide instant results.

[Eugene]

Compression tests. Cold engine prefered.

Dry test first. Remove all spark plugs. Compression tester in #1 cylinder. Ignition switch off. Crank engine over at least 5 full revolutions. Write down the number. Move to cylinder #2, then 3 and 4.

Table spoon engine oil on top of each piston. Crank engine over a couple of revolutions. Then take compression readings again. That is the wet test.

Report the test readings.

6 volt battery usually has 3 caps for adding distilled water.

[1cubnow]

@Eugene, thx for this. Do I crank with the starter when testing or crank by hand via fan?

[Eugene]

Use the starter. You will get better readings.

You can hand crank but the compression readings will be lower.

[1cubnow]

Thx @Eugene. Now I just need to get a compression tester. Looks like Harbor Freight has one for pretty reasonable $$. Have you used this ?

https://www.harborfreight.com/compressi ... 62638.html

[Eugene]

Many auto parts stores have loaners. You pay the retail price to take out the instrument/tool. When returned you get your money back.

My opinion. If you are going to use it more than once, purchase quality. Harbor Freight, OK for some items.

[inairam]

If you were able to plow that deep I would not worry about a compression test. Your engine is fine.

[Glen]

Hi,
The Cub operator's manual can help you learn about maintenance that the Cub needs.

Below is the 1955 Cub operator's manual. The experts on here recommend people read it. It has lots of info about operation, maintenance, and lubrication. There is a table of contents on page 1.
It shows how Cubs originally looked in it. The lube section begins on page 21.

http://farmallcub.com/rudi_cub/www.clea ... index.html

They have said on here that IH didn't make a new manual every year.
This manual shows the electrical system that a 1951 Cub originally had.
Cubs made before mid 1964 originally had 6 volt, positive ground electrical systems.

The Touch Control fluid talked about in the manual was changed later to Case IH Hy-Tran fluid. It is sold at Case IH dealers.

I would check or change all the oils before using the Cub. Using it with low oil in a gear housing can damage the parts in the housing.
There are 3 separate gear housings, with 3 separate oil levels to check, in the rear area of a Cub, the transmission, and 2 final drives.

The transmissions in Cubs commonly get water in them, from rain, or condensation inside the housing over time.

The manual above has 2 pages missing in the lubrication section.
Below is the 1950 Cub operator's manual. Look on pages 19, 20, and 21 to see the info missing from the 1955 manual.
Some of the electrical system info in this manual is different than a 1951 Cub originally had, disregard it, and use the 1955 manual.

http://farmallcub.com/rudi_cub/www.clea ... index.html

There is a 1952 Cub operator's manual at the upper left of the page at Quick links, if you would rather have that manual. I can't post it here. Click on Quick links, then PDF Manuals.

People on here have said they use 15W-40 motor oil in Cubs, it may help the engine have more oil pressure.