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I posted in the cub cadet form but maybe this is a better place.

Kohler Command 12.5
Got the Cub Cadet 1320 hydro out the shed after all winter.
New battery today.

Starts - make a horrendous hammering sound - blowing oil & smoke out the exhaust. dies in 10 seconds.

700 hours. Oil & filter changed every 100 hours or so.

My guess is a stuck piston ring. We were in a drought area last year so it probably sat longer this winter than usual.

What to do?

Repair or replace?

It's a horizontal piston engine so pouring something in to try to free up a ring means turning this heavy mower on it's side or end or taking the motor out which is half way to tearing it apart.

Looking around for used motors I see these were installed different brands of mowers. Would they all be interchangeable? Same bolt pattern and shaft size? Fuel line and throttle hook up? Should I look for one that was from a Cub Cadet?

I'm somewhat mechanically inclined and I have had push mowers apart before. Several used motors for $400 ish.

Or is there something at Harbor Freight or Northern Tool that might fit?

rickpaulos said:

I posted in the cub cadet form but maybe this is a better place.

Kohler Command 12.5
Got the Cub Cadet 1320 hydro out the shed after all winter.
New battery today.

Starts - make a horrendous hammering sound - blowing oil & smoke out the exhaust. dies in 10 seconds.

700 hours. Oil & filter changed every 100 hours or so.

My guess is a stuck piston ring. We were in a drought area last year so it probably sat longer this winter than usual.

What to do?

Repair or replace?

It's a horizontal piston engine so pouring something in to try to free up a ring means turning this heavy mower on it's side or end or taking the motor out which is half way to tearing it apart.

Looking around for used motors I see these were installed different brands of mowers. Would they all be interchangeable? Same bolt pattern and shaft size? Fuel line and throttle hook up? Should I look for one that was from a Cub Cadet?

I'm somewhat mechanically inclined and I have had push mowers apart before. Several used motors for $400 ish.

Or is there something at Harbor Freight or Northern Tool that might fit?

View attachment 70629

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Sounds like a search on Ebay for a good use engine might be a solution.

Stay with a similar Kohler CV 12.5S spec 1211 engine.

If you are not accustomed to readapting a different make of engine, this would not be a time to learn the hard way

These engines were installed on many brands of rider mowers but stay with one off of a cub cadet if possible.

These Kohler engines were manufactured too the mower manufacturers specifications.

Yeah I checked the Kohler engine parts site and they listed cub cadet specific piston rings for the Kohler Command 12.5 hp motor.

I've yet to do anything. I think the next step is a compression test.

A friend suggested some sort of solvent/cleaner in to the piston but this is a horizontal cylinder engine so I'd have to stand the mower on end to get any fluid to the rings.

Unless I really had some attachment to the machine, or it is in very good shape, I certainly wouldn't spend 500 to repair it. Did the smoke and noise begin immediately when it started, or did it run ok for a couple of minutes before the failure? It isn't a stuck ring, as that would not cause any hammering. Unusual for a command to crap out at 700 hrs. 100 hr. oil changes is pushing it with conventional oil on a 35-yr old engine. I would pull the valve cover off and see whats going on with the top end since it is blowing smoke.

Yes, noise and smoke and oil on the first start for the season. Been in an unheated shed all winter like it is every winter. I've been looking locally for similar mowers. Nothing yet that appeals to me. I've seen some 1320's for sale in the past few years for cheap. I have the bagger for the 1320 that I do use for leaves in the fall.

rickpaulos said:

Yes, noise and smoke and oil on the first start for the season. Been in an unheated shed all winter like it is every winter. I've been looking locally for similar mowers. Nothing yet that appeals to me. I've seen some 1320's for sale in the past few years for cheap. I have the bagger for the 1320 that I do use for leaves in the fall.

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I found several engines specific to that machine on eBay if you wish to go that route. The thing is you have no idea how they were maintained. But that is your best route. However, I find it very strange that your engine failed. I wonder if something got sucked in from the carb, such as a throttle plate or choke plate screw. Last summer I had a machine in the shop where that happened. Inside the head and top of the piston were banged up fairly good, but no damage...put a new head gasket on it after removing the screw, and she ran/runs fine. I would first pull the valve cover off to have a look before spending money. If you have basic mechanical abilities, pull the whole thing apart, find the failure, and repair it. They are fairly simple to work on. Good luck to you.

before you do all of that if it did not do that when you put if up for long term storage, I would guess that the fuel when by the needle and into the fuel thinning it and over filling it, it has no room to breathe, drain the oil for a day or so, when you add oil don't over fill, change the plugs, if you still have missing take the coils off sand the surface and the mounting post, to assure a good ground they try it, it is not the rings.

rickpaulos said:

I posted in the cub cadet form but maybe this is a better place.

Kohler Command 12.5
Got the Cub Cadet 1320 hydro out the shed after all winter.
New battery today.

Starts - make a horrendous hammering sound - blowing oil & smoke out the exhaust. dies in 10 seconds.

700 hours. Oil & filter changed every 100 hours or so.

My guess is a stuck piston ring. We were in a drought area last year so it probably sat longer this winter than usual.

What to do?

Repair or replace?

It's a horizontal piston engine so pouring something in to try to free up a ring means turning this heavy mower on it's side or end or taking the motor out which is half way to tearing it apart.

Looking around for used motors I see these were installed different brands of mowers. Would they all be interchangeable? Same bolt pattern and shaft size? Fuel line and throttle hook up? Should I look for one that was from a Cub Cadet?

I'm somewhat mechanically inclined and I have had push mowers apart before. Several used motors for $400 ish.

Or is there something at Harbor Freight or Northern Tool that might fit?

View attachment 70629

Click to expand...

One thing to do I have seen it happen, check or drain your fuel. A fellas son accidently put kerosene from a gas can in the tank. the motor was rebuilt, same problem. The customer bought a new engine, same thing, smelled the fuel, gas mixed with kerosene. Drained the fuel, blew out lines changed the filter, good to go.

rickpaulos said:

I posted in the cub cadet form but maybe this is a better place.

Kohler Command 12.5
Got the Cub Cadet 1320 hydro out the shed after all winter.
New battery today.

Starts - make a horrendous hammering sound - blowing oil & smoke out the exhaust. dies in 10 seconds.

700 hours. Oil & filter changed every 100 hours or so.

My guess is a stuck piston ring. We were in a drought area last year so it probably sat longer this winter than usual.

What to do?

Repair or replace?

It's a horizontal piston engine so pouring something in to try to free up a ring means turning this heavy mower on it's side or end or taking the motor out which is half way to tearing it apart.

Looking around for used motors I see these were installed different brands of mowers. Would they all be interchangeable? Same bolt pattern and shaft size? Fuel line and throttle hook up? Should I look for one that was from a Cub Cadet?

I'm somewhat mechanically inclined and I have had push mowers apart before. Several used motors for $400 ish.

Or is there something at Harbor Freight or Northern Tool that might fit?

View attachment 70629

Click to expand...

That does sound like the gas tank drained into the crankcase. Possibly the noise is fuel igniting in the exhaust. Even after you change oil it will smoke for another 5 to 10 minutes cleaning out the muffler. Another possible noise is this engine has hydraulic lifters and may not have enough oil pressure because of all the gas in the oil, again letting it run should push out the thinned out oil from the lifters. The Kohler Command you have is one of the few that will out last the tractor . On another note the engine bolt pattern , crankshaft size/length fuel line are not a problem. Depending on the donner engine ,does your tractor have a independent chock cable that you pull or is it part of the throttle? The exhaust might have to be a screw in after market muffler ? The charging system on the donor might be a one wire with a diode and yours is a Regulator Rectifier which has two A/C wires from the stator and is converted to DC and regulated to 13.8 volt to the battery . You have our interest so keep us informed.

Simply remove the carb and check the throttle and choke plates for missing screws first. Something got inside the cylinder.

Rocky J said:

That does sound like the gas tank drained into the crankcase. Possibly the noise is fuel igniting in the exhaust. . You have our interest so keep us informed.

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DING DING DING, We have a winner. Thank you Rocky J.

Now that it's warm enough outside to work on it. I spotted some fluid under the front left of the mower as I pushed it back out side. Right below the carb. First up, drain the crank case and about 1 gallon of gas & oil came out.
This is the first time I've even heard of that happening in any small motor.

I'm assuming it's the float needle that leaked. On this carb the needle does not have the rubber tip, there is a sea green seal in the top of the needle port. I'll be looking for a carb kit with that type of seal. I assume it's just pressed in. Float bowl gasket is rather hard.

Will clean up the carb, add new oil and try it....

Walbro LMK12798 1205301 There are some other numbers that probably don't matter.

Not finding a LMK12798 or is that model "LMK" with a date after it? This Cub is listed as 1989 to 1991 on TractorData dot com
I bought this new in October 1990 - end of season sale. So maybe a typo on the carb date. 98 vs 89.


Gezze there are countless carb kids. Gravity feed. Would need carb-to-block gasket & carb-to-air-filter gasket, float bowl rim gasket, needle, seat.

The jet is slightly off center. Looks like it's pressed in. I'll just try to bend it back.

Carb cleaned and reassembled. New oil and filter. Cleaned the spark plug. I did try to straighten out the jet but it just springs back to where it is. Didn't want to risk breaking it off or breaking off the tool inside it. (dental pick)
Started right up and sounds fine. Blew lots of smoke as stated. Let it warm up for a couple minutes then mowed off the pampas grass. Smoked a lot for about 10 minutes then quit smoking. Ran fine for the 30 minutes I used it.

Need to get a carb kit if I can figure out which it needs. I'll change the oil again when that kit arrives.
I plan on adding a shut off valve to the fuel line.

You can look up the carb via the engine model and spec (link to parts here). To get the seat out, blow compressed air into the fuel inlet and hold your finger very slightly away from the hole to catch it. Use the reverse side of the needle jet to press the new one in. If it is gravity-fed, the carb kit part number is Kohler 12 757 01-S. If it has a fuel pump, the kit is part number Kohler 12 757 03-S

rickpaulos said:

Carb cleaned and reassembled. New oil and filter. Cleaned the spark plug. I did try to straighten out the jet but it just springs back to where it is. Didn't want to risk breaking it off or breaking off the tool inside it. (dental pick)
Started right up and sounds fine. Blew lots of smoke as stated. Let it warm up for a couple minutes then mowed off the pampas grass. Smoked a lot for about 10 minutes then quit smoking. Ran fine for the 30 minutes I used it.

Need to get a carb kit if I can figure out which it needs. I'll change the oil again when that kit arrives.
I plan on adding a shut off valve to the fuel line.

View attachment 70729

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Looks like you're putting the old girl to work! Tough machines for what they were. I have a 1989 Wheel Horse 212-H with 3200 hours on it, and the thing won't die no matter what I do to it. The old Briggs 12 hp flathead rattles like heck but has for 15 years. I bought a replacement engine for it back in 2012, as I thought it wasn't long for the world, but I put about 40 hours a year on it, and it just won't die! Tranny is a beastly Eaton 750, and it doesn't have enough power to ever hurt it. Love old machines. Some of the new stuff I get in the shop is just sad...grab the rear fender to slide it or push it, and it bends like a piece of solder.