Cub Cadet 123: head differences, damaged bore, hydrostatic leak

[knucklescraper]

Hello. I am a new forum member. If I have posted in the wrong place or
should have posted separate questions, please let me know.

I acquired a cub cadet model 123 with a Kohler K301AS engine s/n C020835 spec no. 4759B about a year ago and have been fixing it up (see attached photos 01 and 02).

I recently swapped engines due to the connecting rod breaking in the original
and taking a chunk out of the cylinder wall. The replacement engine K301A
s/n E0009326 spec no. 47138B has a block with studs for the head. My original K301AS had no studs. I have attached photos of the two heads (see photos 03 and 04). I decided to use the head that came with the replacement K301A engine, that is, the one meant to be used with the studs. After I installed the head (see attached photos 05 and 06), I realized that the thin sheet metal
plate and thicker plate (see attached photos 07, 08, 09, 10) no longer fit. I started to modify them to accomodate the new spark plug location but then realized that there is insufficient space vertically on the studs if I use the spacer bushings that came with the engine. I could use shorter bushings but maybe this affects rigidty/stiffness of the installed head?

(1.) Is it safe to run the engine without using these plates?
I'm not sure if their main purpose is heat transfer or protecting the head
from damage or what. I also don't know in general why Kohler changed from
using no studs to using studs and bushings.

(2.) Is there an advantage to using one head versus the other due to spark
plug location or because of the studs or some other reason? The head from the studded block has the spark plug aligned over the exhaust valve. The head from the block without studs has the spark plug located in between the two valves.

So the options I can think of are to use the head meant for the studs without
installing the plates (that's the way I have the tractor now), use this head with modified plates and shorter bushings, or use the head from the original engine and install the plates.

Additional questions not related to the head.

(3.) If the chunk missing from the cylinder bore from my first engine
(see attached photo 11) is below the max travel of the piston, can that
block be re-used, maybe after dremeling the edges?

(4.) I have a hydraulic fluid leak coming from the hydrostatic transmission.
It is a slow leak coming from some point near the top of the unit (see
attached photos 12 and 13) but I can't determine exactly where. The tractor
had been running for months without leaking. I first noticed it over the winter when I wasn't using the tractor and before the connecting rod broke. Has anyone used Lucas stop leak with success? The container says it is 100% petroleum and it looks like really thick oil. I'm not sure what else to try short of splitting the tractor. But even if I do that and find the spot it is leaking from, I'm not sure I want to tear into the hydrostatic transmission. I think it is beyond
my skill level.

Any comments are welcome. Apologies for the long post. I assure you it took
me far longer to write it than for you to read it.

[West Valley G]

I don't have any idea on your questions about the heads. Have not
seen one with the studs.
However at least one good possibility on the hydro leak would be the
cork gasket. Sits behind the charge pump on the hydro. It is actually
a pretty simple fix but you will have to split the tractor to get to it.
Splitting seems like a more ominous task then it really is. You will not
have to get inside the hydro pump. It is an easier job then most of the
engine work your doing. Good luck
Ken


DSCN1993.jpg

DSCN1996.jpg

[R Bedell]

First, welcome to OCC...........

I acquired a cub cadet model 123 with a Kohler K301AS engine s/n C020835 spec no. 4759B

That engine was NOT specified for Cub Cadet. It was an aftermarket version.

The replacement engine K301A s/n E0009326 spec no. 47138B

That IS a Cub Cadet specified engine.

The "plates" or shrouds are for air flow and cooling of the Kohler Engine.

(1.) Is it safe to run the engine without using these plates?

The engine will run hotter and NOT a good idea unless you are in Alaska.

(2.) Is there an advantage to using one head versus the other due to spark

I would keep the head that came with the engine. When looking for parts in the future, it is so much more simple by looking up a K301-47138 and knowing all the parts are original.

(3.) If the chunk missing from the cylinder bore from my first engine
(see attached photo 11) is below the max travel of the piston, can that
block be re-used, maybe after Dremeling the edges?

I have done it on a Kohler KT-17 with NO issues.

West Valley covered the Hydro issues.

[knucklescraper]

West Valley G / Ken,

That seems a likely place to look.

I found these images in the hydrostatic service manual. I suppose any of these seals could be the culprit. Is this the area you mean?

Also, thanks for your encouragement. I will probably split the tractor for a closer look. I'd rather not put goop in the transmission.

[knucklescraper]

R Bedell,

That's interesting that the engine I took out was not an original Cub Cadet engine. I had no idea. I had assumed everything was original. I got it from my neighbor but he hadn't used it in decades and didn't remember much about it. He bought it used in the early 70's. I also have no idea if the head that came with the engine K301A engine I recently bought is the original.

I'll hang on to the block in case I need it down the road since you were successful with yours.

Thanks for the tip about searching with K301-47138. I just did that to find the parts diagrams on Kohler's website. I looked at the diagrams for the shrouds and the head. I'm a little puzzled by both of them. The one for the shrouds is here: https://kohlerenginesparts.com/oempa...-10-10-tp-2097 and the one for the head is here: https://kohlerenginesparts.com/oempa...r-head-tp-2097

The diagrams seem to show two different heads and two different shroud configurations and none of the shrouds look like heavier plate version I have. Maybe the parts changed over time and the diagrams are trying to depict that.

I think I'll search around on this forum for someone who posted model 123 photos so I can see what the head/shrouds should look like.

For the short term, I might finish modifying the shrouds from the K301AS engine and install shorter bushings on the studs so the shrouds fit. It is kind of neat how the air flow from the fly wheel is used to cool the engine.

I'm new to cub cadets but their simplicity, ruggedness, and mechanical ingenuity are growing on me. I like that a 50 year old tractor/engine is still running. I assume the K301A was rebuilt once because it has .003 stamped on top of the piston but it's still a long life.

Thanks for your reply.

[West Valley G]

Oops. I was thinking about the charge pump gaskets which you
show because I have seen em leak. But the cork gasket which is the
most likely culprit is not where I described. Sorry for the bad lead.
Here is a better picture of the cork gasket. Between the hydro and the rear
end.DSCN1923.jpg

Ken

[knucklescraper]

darkminion_17,

Agreed, shorter spaces are necessary. I worked out the necessary sizes earlier today. The current spacers are 0.716" long (~23/32"). The two suporting the thicker plate will need to be ~1/4" shorter and the three under the gas tank will need to be ~3/8" shorter. I'll do some shopping.

ironman,
Thanks for the photos. Those are some beautiful tractors. The head you labeled 4th gen is the one I mounted to the K301A engine that I just put on the tractor. I bought that engine (with that head) from somenone on Craigslist earlier this month so I had no idea if it was the proper head. I'll continue with that head under the assumption that a 4th gen design is an improvement over a 3rd gen design. Maybe moving the spark plug provides more efficient combustion. I'm curious what benefit the studs/spacers add.

After I figured out the modifications I'd need for the baffle (thin plate) and shroud (thicker plate) and spacers earlier this afternoon, I then went ahead and split the tractor in preparation for finding the hydraulic leak.

I had some trouble getting the cotter pin out of the brake linkage rod. But that was nothing compared to the trouble I had trying to pull the tractor halves apart. I didn't have very good chucks under the front wheels so I kept dragging the whole tractor back every time I yanked on the rear. I was also using jacks and jack stands trying to shift the weight off the rear. But that usually raised the rear too.

There is a pin in the tow bar release lever that got caught on a nut on top of the hyrdo unit. I marked the nut up a bit before I noticed. Younger me would have just kept yanking and driven the pin into the hydraulic tube behind it. Even so, I came close to doing just that. I eventually had some arrangement of jacks and jackstands that had allowed the proper clearance. I separated the tractor by sitting on the ground behind rear, putting my feet on the frame and yanking on the rear axles. I had to be quite careful because the drawbar was aimed at a sensitive part of my anatomy.

Tomorrow's plan is to clean off the leaking hydraulic oil and try to find its source.
Once I find it, I probably have to remove the hydro unit to replace a seal or gasket. Is it possible to do that without draining the hydraulic fluid? Maybe by rotating the whole rear end 90 degrees upward from its normal orientation so the oil drains down into the differential housing and out of the hydro? That's what I'm thinkiing of trying anyway.

By the way, my tractor serial number 193356. Does that mean anything?

It's already tomorrow. TIme for bed.

[finsruskw]

That number means it was built in March of 1967

[West Valley G]

Glad you got the tractor split. Like I said it's not too ominous. I guess
maybe I should have given a description of ominous
Just think how easy it will be next time. I promise.

Ken

[knucklescraper]

West Valley G,

You called it. I think the leak is coming from that cork gasket. It is seeping very slowly (now that I want it to leak).


Back on the head and spacer issue...
I was looking at that again yesterday. I may have created my own problem.
Before I installed the head, I had watched an online video in which the guy used the stackup shown in the sketch "current hardware stackup" in the attached pdf file. So that's what I did.

Question: Do you guys that have heads with studs use a double nut stackup (nut - spacer - nut)?

It is probably not an accident that the spacer height is the same as the distance from the boss to the top of the fin. So now I'm thinking maybe the correct hardware stackup is what I sketeched in "solution #2". I only wonder why Kohler wouldn't have simply changed the boss head height to bring it even with the top of the fins?

EDIT: I think the pdf file was too large and it didn't upload the first time. I reduced its file size (and its quality) and re-uploaded it. I also attached a photo of the sketch. I don't know which is easier to read.