M18 Oil Pressure issue

[ol'George]

Originally Posted by mobermiller

Thanks ol'George for your insight to my problem.

I'll share some history that I have discovered as I have progressed with my investigation of what's going on.

First of all I bought this super as a 2072 from a person I have known for over 40 years. He told me it had the M20 engine in it and I had no reason to doubt him. 20 years ago he had bought an 1872 and shortly after he bought it, a screw that holds the air filter assembly to the elbow on the carburetor came loose and got sucked into the # 1 cylinder. This screw got embedded into the top of the piston. He took the head off and found the screw and removed it. As of last summer, he was still using this engine in that same 1872, according to him.

When I pulled the engine out of this 2072, I discovered it had an M18 in it. I really didn't think much about it because a previous owner could have switched hoods or replaced the engine. The engine ran good with no smoke and no knocking.

While the engine was out I removed the heads and guess what I found on top of the number 1 piston? A nice dent left by a screw!

Moral to the story, Even someone whom you may trust, will still put the screw to you!

The engine only has 75 psi of compression in each cylinder. Both pistons are loose in the cylinders. I'm convinced this engine is wore out and I'm just going to put it back together and use 40 or even 50 weight oil in it and run it till it runs no more. I will be looking for a command engine to put into my 72 series super this winter.

Thanks for the help!

If both cyl's have #75 it sounds like it has higher hours on it, and is prolly pushing a bit of oil in the air cleaner, but not slobbering.
It's been my experience #95 is normal.
Sounds like the "screw" didn't do a lot of damage or it would of long since died.
If you are comfortable with not rebuilding it go ahead and use it.
I'd run #30W oil and continue not abusing it, and it just might live a long time.
A little oil usage is to be expected, just keep it full and not neglected.
It is obviously getting oil, just loosing pressure because it is worn.
I like those engines as most here know.
They got an undeserved rap because of the series 1 predecessors.
Truth be told, they will and have run longer than some of the later OHV designs, under the same conditions.
They are smooth and torquey,
I doubt a person uses 20 hp in a super
Enjoy it.

[Gompers]

Originally Posted by mobermiller

Thanks ol'George for your insight to my problem.

I'll share some history that I have discovered as I have progressed with my investigation of what's going on.

First of all I bought this super as a 2072 from a person I have known for over 40 years. He told me it had the M20 engine in it and I had no reason to doubt him. 20 years ago he had bought an 1872 and shortly after he bought it, a screw that holds the air filter assembly to the elbow on the carburetor came loose and got sucked into the # 1 cylinder. This screw got embedded into the top of the piston. He took the head off and found the screw and removed it. As of last summer, he was still using this engine in that same 1872, according to him.

When I pulled the engine out of this 2072, I discovered it had an M18 in it. I really didn't think much about it because a previous owner could have switched hoods or replaced the engine. The engine ran good with no smoke and no knocking.

While the engine was out I removed the heads and guess what I found on top of the number 1 piston? A nice dent left by a screw!

Moral to the story, Even someone whom you may trust, will still put the screw to you!

The engine only has 75 psi of compression in each cylinder. Both pistons are loose in the cylinders. I'm convinced this engine is wore out and I'm just going to put it back together and use 40 or even 50 weight oil in it and run it till it runs no more. I will be looking for a command engine to put into my 72 series super this winter.

Thanks for the help!

If you haven't been intimate with an M20, they look pretty similar to the 18s from the outside, but they have different tins that "bulge" around the heads to accommodate the engine's longer stroke. Once you've seen them side by side, it's easy to spot a 20.

If you're looking to rebuild, the 18 will be a lot easier to find parts for.

The KT17 S1 only had about 5 PSI of pressure and the same basic design as your M18 and they can last a long time, even without an oil filter. I just picked one up in an early MTD 782 the other day and it's one of the better running KTs I've had, though I'm not sure if it's been gone through or how recently.

For what it's worth, while most KT and Mag engines have that oil pressure port, up until the 1810/11/12, it wouldn't have been used on a Cub Cadet. That includes all of the 682s and 782s ever built by IH/CCC. Not saying that it's a good thing to have low pressure, but it's not 100% sure to kill the engine immediately or anything, and sometimes ignorance is bliss.

If you can swing it, move that engine on to someone who wants to rebuild it before it throws a chunk of rod out the side of the crankcase and swap in a CH20 or vanguard.

I've also grown to like these engines.

[ol'George]

While the series 1 is the same basic design, the oiling system is where it lacks.
It does share the same oil pump as the series 2 and magnum, but does not have an oil pressure relief spring, thus the low pressure.
Also the crank is not cross drilled to pressurize the rod journals, they rely on 2 drilled holes in the hollow camshaft to squirt oil toward the rod journals every other crankshaft revolution ( camshaft turns 1/2 crank speed)
so, while many are still running, it is not as desirable a system, compared to the improvements that the series 2/mags have.
Also the 2 and mags, have more and heavier webbing in the block as well as the mags have a larger diameter crank at the oil seal area for flywheel support.
As the Kohler engines were used in many applications like skid steers etc. they felt a need to strengthen that area of the crank.
I would not consider a series 1 as a replacement engine, but a series 2 and magnum would be a nice bolt in.
Understand,
i have nothing against fellows going to modern OHV designs.

[J-Mech]

Originally Posted by Gompers

For what it's worth, while most KT and Mag engines have that oil pressure port, up until the 1810/11/12, it wouldn't have been used on a Cub Cadet. That includes all of the 682s and 782s ever built by IH/CCC.

I guess I don't understand this statement.
Cub Cadet used the KT I in the 82 series, but the late 82's had the KTII which did have a pressure lube system. The Mag motors (Same as a KTII only with magneto ignition) was used until the 1811 series tractors which included the 1872. So... yes, CCC used the pressure lube engine. Actually, CCC only used the KTI for a short time before they moved on to the better engine.

And yes, low oil pressure in a pressure lube engine will kill it. The KTII and Mag engines (as George has explained well) used a completely different lube system, so you cannot compare the oil pressure in a KTI to the II or M motors. They are apples and oranges.


To the OP:
FWIW, a pressure drop once heated up, is not all that uncommon, but it shouldn't go that low. I would replace the oil filter lines and the pressure regulator valve and see if that fixes it.

[Gompers]

Originally Posted by ol'George

While the series 1 is the same basic design, the oiling system is where it lacks.
It does share the same oil pump as the series 2 and magnum, but does not have an oil pressure relief spring, thus the low pressure.
Also the crank is not cross drilled to pressurize the rod journals, they rely on 2 drilled holes in the hollow camshaft to squirt oil toward the rod journals every other crankshaft revolution ( camshaft turns 1/2 crank speed)
so, while many are still running, it is not as desirable a system, compared to the improvements that the series 2/mags have.
Also the 2 and mags, have more and heavier webbing in the block as well as the mags have a larger diameter crank at the oil seal area for flywheel support.
As the Kohler engines were used in many applications like skid steers etc. they felt a need to strengthen that area of the crank.
I would not consider a series 1 as a replacement engine, but a series 2 and magnum would be a nice bolt in.
Understand,
i have nothing against fellows going to modern OHV designs.

George I know there are at least two different SII crankcase castings, one with oil filter and one without. Do you know if both of them have the additional webbing?

Also, do you know if the later SII (with bypass/oil filter provision) casting is identical to the M18 casting aside from being drilled for the points?

I know they were making KTs up until the 90s, and I can't imagine they would be making both engines with two different crankcase castings when they are identical.

[Gompers]

Originally Posted by J-Mech

I guess I don't understand this statement.
Cub Cadet used the KT I in the 82 series, but the late 82's had the KTII which did have a pressure lube system. The Mag motors (Same as a KTII only with magneto ignition) was used until the 1811 series tractors which included the 1872. So... yes, CCC used the pressure lube engine. Actually, CCC only used the KTI for a short time before they moved on to the better engine.

And yes, low oil pressure in a pressure lube engine will kill it. The KTII and Mag engines (as George has explained well) used a completely different lube system, so you cannot compare the oil pressure in a KTI to the II or M motors. They are apples and oranges.


To the OP:
FWIW, a pressure drop once heated up, is not all that uncommon, but it shouldn't go that low. I would replace the oil filter lines and the pressure regulator valve and see if that fixes it.

I was talking about the oil pressure port. IH/CCC used horizontal twin KT engines without oil pressure sensors, so you would never have known what kind of oil pressure you had unless you put a gauge on it, which it didn't come with. I'm sure a lot of engines died from low/no oil pressure over the years, which is for sure one of the main reasons for the oil sentry in later engines, but I'm sure a good deal of them have oil pressure issues that ran for a good long time before they blew.

[J-Mech]

Originally Posted by Gompers

I was talking about the oil pressure port. IH/CCC used horizontal twin KT engines without oil pressure sensors, so you would never have known what kind of oil pressure you had unless you put a gauge on it, which it didn't come with. I'm sure a lot of engines died from low/no oil pressure over the years, which is for sure one of the main reasons for the oil sentry in later engines, but I'm sure a good deal of them have oil pressure issues that ran for a good long time before they blew.

They all had the pressure port. They just didn't all have a pressure sending unit/oil light. None of them had a sentry system, as CCC didn't use a low pressure shut down on any of their machines. As I recall, the light didn't come on until pressure was below 5 psi.

[Gompers]

Originally Posted by J-Mech

They all had the pressure port. They just didn't all have a pressure sending unit/oil light. None of them had a sentry system, as CCC didn't use a low pressure shut down on any of their machines. As I recall, the light didn't come on until pressure was below 5 psi.

Kohler referred to the sending unit and wiring (3rd wire on the harness) as "oil sentry". The system on the 1800 series is also referred to as "oil sentry" even though it doesn't shut down the engine. It was up to the manufacturer what to do with the low oil pressure sensor. CCC just decided to put a light on the dash instead of putting in a circuit to kill the engine.

On my 682 M18 swap, I wired in a 10s time delay relay to kill the engine if the oil sentry switch senses low oil pressure (~3.5 PSI per the service manual) since I wanted to keep the dash factory stock but still have some protection from low oil pressure.

[J-Mech]

Yes, I understand what the books call the oil pressure switch system. But just like the part books call the magneto an "ignition module" there is nothing about that part that is a "module". It is still a magneto no matter what the book calls it.

[ol'George]

Originally Posted by Gompers

George I know there are at least two different SII crankcase castings, one with oil filter and one without. Do you know if both of them have the additional webbing?

Also, do you know if the later SII (with bypass/oil filter provision) casting is identical to the M18 casting aside from being drilled for the points?

I know they were making KTs up until the 90s, and I can't imagine they would be making both engines with two different crankcase castings when they are identical.

I can't tell you if the last Kt blocks were the same as mag blocks as I don't have a late kt block to compare to a mag block.
I do know they eliminated gaskets and went to RTV sealant,and caution that if the pto cover had a gasket, to reinstall with one.
That would indicate the .020 or so gasket thickness, was taken care of in the cover, not the block.
I personally don't think it is critical as far as the cover with or without a gasket.
I think the series 2 had the thick webbing but can't swear to it.
Don't disrespect a series 2 block without an oil filter provision.
Production went to many manufactures that didn't request/require it so it was not provided by Kohler.

The jugs on the late mags went to a *30 valve & seat angle.
Also the right & left jugs were different in at least 2 ways.
One for a magneto mounting, also a hardened valve seat for the exhaust valve.
So while the jugs will bolt on, they would not have the correct valve seats and the mounting holes for magneto mounting.
IIRR also the camshaft has a different part number for the *30 valves
it is covered in the service manual.
But again I don't see why either cam will not work in either magnum block.
other than the mag cam has no lobe for ignition point activation if installed in a kt block.





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