everything Kohler k series

[Donleecampbell 3]

let me start by saying thank you for letting me Join the site. I was hoping I could get some info on everything about the k series and magnum series kohlers. I am going to try to rebuild a m12 in a 312-8. I thought about looking for another engine , but didnt know if they all had the same pto shaft size or were brand specific. I also was wondering if any of the engines in the wheelhorse 300, 400, 500 series would be a direct swap into my 312 ? I sold a 317 years ago and regretted it ever since. lol. I went to buy a wheelhorse plow to modify for my Bolens large frame and when I told the guy what I planned on doing with it, he said i will sell you the tractor for 50 bucks !!! it was beautiful. he started it up and it smoked and had no power. he explained it was tired. needless to say i snatched it up!! mower deck is in great shape. all of it was stored in a barn. the guy said im really tired and have enough projects. i said thank you jesus and went home happy, lol. now i need to gather as much info on these as I can. thanks for reading my post . edit thought someone may find this info useful. it was posted by Brian Miller..

Differences Between the Kohler K-series and Magnum Engine Blocks -

Unlike the old school small- and big-block Chevy V8's, the Kohler K-series and Magnum engine block models K241, M10, K301, M12, K321, M14, K341 and M16 are not all the same. There are several variations in bolt patterns and PTO end flange configurations between these blocks. Before replacing an engine block and if possible, the best thing to do is have the original engine rebuilt, then all the original accessories will attach to the original block with no modifications. But if the original engine block is not rebuildable and damaged beyond repair, another block of the same type (specification number) will need to be acquired. If interested in purchasing a bare block, please email me several detailed, sharp photos of your original engine block taken at all sides so I match it to one I may have in stock. Packaged shipping weight for each bare block is 45 lbs.

The Major Differences Between the K241, M10, K301, M12, K321, M14, K341 and M16 Kohler Engine and Blocks -

• The K241 and M10 blocks have a STD cylinder bore of 3.250" and the stroke is 2.875". All of these blocks have an exhaust valve diameter of 1.125" and the intake is 1.375". Some rare K241 blocks have "K301" embossed on the PTO end. These have a thicker cylinder wall than ordinary K241 blocks.
• The K301 and M12 blocks have a STD cylinder bore of 3.375" and the stroke is 3.250". There are no other major differences between these two blocks. These blocks have the same size valves, and most external parts will interchange. Due to the smaller cubic inch displacement, which lessens the amount of air that enters the engine, theses engines use a Carter or Kohler #26, or Walbro #52 (1.07" throttle bore) carburetor.
• The K321 and M14 blocks have a STD cylinder bore of 3.500' and the stroke is 3.250". There are no other major differences between the K241, M10, K301, M12, K321 or M14 engines. The early K321 blocks have an exhaust valve diameter of 1.125", and the valves in the later K321 blocks are the same diameter, which is 1.375". Some internal, but most external parts on the K241, M10, K301, M12, K321 and M14 engines will interchange, with the exception of the early style K241 cylinder head and size of the carburetor. Due to the larger cubic inch displacement, which increases the amount of air that enters the engine, the K321 and M14 engines use either a larger Carter or Kohler #28 or #30, or Walbro #60 (1.17" or 1.2" throttle bore) carburetor.
• The K341 and M16 blocks have a STD cylinder bore of 3.750" and the stroke is 3.250". There are no other major differences between the K241, M10, K301, M12, K321, M14, K341 or M16 engines, except the valves are the same diameter, 1.375". And the K341 and M16 blocks have 10 cylinder head bolts. Due to the larger cubic inch displacement, which increases the amount of air that enters the engine, the K341 and M16 engines also use a #30 (1.2" throttle bore) carburetor. And most external parts, except the cylinder head and air shields, will interchange with the K241, M10, K301, M12, K321, M14, K341 and M16 engines.

The Major Differences Between the Kohler K-series and Magnum Engine Blocks -

Some Kohler blocks have wide base flanges (for the wide, deep oil pan) and some have a narrow base with no flanges. (These are used on Cub Cadet, Ford, certain John Deere and Wheel Horse garden tractors.) Most Magnum blocks are wide base, and very few are narrow base. The very early K241 10hp blocks have no indentation for installing an upper mount gear starter (mounting bolts are below the starter motor). Also, some of these older blocks with flanges have no holes drilled for converting to a narrow base oil pan. (But holes can be drilled and tapped.) Some blocks have either a drilled or threaded oil dipstick tube hole next to the cylinder, above the crankcase, while others have no hole present. Some blocks have provisions for a starter-side oil dipstick tube, and some don't. Some blocks came with counterbalance gears and some didn't. Some have expansion plugs where balance gear stub shafts can be installed, and although certain blocks have the bosses, some have no holes drilled for the stub shafts. All Kohler Magnum blocks have no provisions for ignition points.

Some blocks have two threaded holes for installing an exhaust pipe flange, and some don't. Some blocks have provisions to install a mechanical fuel pump, and some don't. Some blocks have different bolt patterns on the PTO end, and Gravely blocks have a raised circular flange. (See below.) Some K241 blocks with K301 embossed on the PTO end have a thicker cylinder wall, and some K241 blocks without the K301 embossing have an ordinary thickness cylinder wall. The 12 fin K341 blocks have an ordinary thickness cylinder wall, and the 13 fin K341 blocks have a thicker cylinder wall. Other than all of the before mentioned È, everything else on the Kohler K-series engine blocks are pretty much the same.

The Differences Between the Old Kohler K-series and the Newer Kohler Magnum Engines -

The Magnum engines replaced the K-series in later years. The Magnum engines are basically the same engine as the K-series. The main differences are, besides the baffle shields (sheet metal) that covers the block, the Magnum has solid state ignition, a fixed main jet (Walbro) carburetor and the starter fastens to the OEM bearing plate instead of the engine block. And there are no provisions for using ignition points. Most of the external and all the internal parts are interchangeable, and most aftermarket (high performance) parts are interchangeable with either engine.

  

A Kohler K-series and Magnum M10, M12, M14 and M16 single cylinder engines will fit in place of a Kohler K241 or M10 engine. These all basically have the same external dimensions, with the exception of the 16hp, which has a larger cylinder. Kohler engines are like the old school small block or big block Chevrolet V8 engines. A small block 400 CID engine can be used in place of a 265 CID engine, and a big block 572 CID [crate] engine can be used in place of a 366 CID [truck] engine, because they basically have the same external dimensions. The main difference with Kohler engines is the bolt patterns on the PTO end of the block. Each block is made specifically for the garden tractor, small motorized vehicle or lawn and garden equipment it goes in. When replacing an engine block with another, make sure the bolt pattern matches that of the original block so the PTO accessories, braces and brackets can be bolted on with no modifications.

The Kohler Magnum engine models M10, M12, M14 and M16 can be used in any Cub Cadet garden tractor. The majority of the Magnum 10-16hp single cylinder engines have flanges at the base. Therefore, the block will need to be converted into a narrow base by cutting off the flanges on each side and then cut new threads in the holes in the block for the narrow oil pan. And the other parts that's needed are: a K-series large OEM bearing plate with an upper mount gear starter (mounting bolts are below the starter motor), or a small K-series OEM bearing plate with a starter/generator; a small or large diameter K-series flywheel with a matching flywheel shroud and baffle shields (sheet metal); and being there's no provisions for ignition points and no points lobe on the Magnum camshaft, Kohler's Breakerless Ignition or crank trigger ignition will need to be used. Also, because of the 3/8" flywheel retaining bolt, an aluminum clutch hub adapter with a 3/8" hole will need to be used, acquire a 5/8"-3/8" reducer/step washer. (I make these.) Everything else should fit in the tractor with no problems.

Only eight models of the 10-16hp Kohler Magnum single cylinder cast iron block engines was manufactured as a narrow base. The specification numbers for these are as follows: M10, specification #'s 461509, 461534 (Cub Cadet garden tractor model 1050); M12, specification #'s 471512, 471514, 471570 (Cub Cadet garden tractor model 1210); M14, specification #'s 601512, 601513; and M16, specification # 711536. All other 10-16hp Magnum engine block specification numbers are a wide base.

 Any Kohler Magnum single cylinder 10-16hp engine would be excellent to pull with. The only problem is, being these come with solid state ignition, with no provision for ignition points, if a steel flywheel is going to be used, a crank trigger ignition system will be needed, too. Also, if the engine has counterbalance gears, they will definitely need to be removed because one or the other could break, destroying the block and other parts. For most engines, it does absolutely no good to reinstall them. Most Kohler engines don't come with them and in most engines, they do very little to reduce engine vibration. When left out, the engine should not vibrate more than usual. Being balance gears are made of cast iron material and operate [out of balance] on a single, narrow needle bearing for support, they've been known to break and destroy the crankshaft, camshaft and engine block. I've seen this happen to a good engine a few times. Therefore, I highly recommend leaving them out. But if the engine vibrates excessively with the absence of the balance gears, the flywheel and/or crankshaft will need to be dynamically and precision spin-balanced to reduce engine vibration. Click or tap here to learn more about flywheel and/or crankshaft balancing. For a steel flywheel, visit Midwest Super Cub's website.

How to Convert a Single Cylinder Kohler K-Series Engine into a Magnum Engine -

To convert the Kohler K-series K241, K301, K321 or K341 engine into a Magnum M10, M12, M14 or M16 engine, the parts that's needed are: Magnum OEM bearing plate; starter motor (the support brackets for the starter are for mounting of the starter solenoid only. They do not support the starter motor whatsoever); flywheel (w/external magnet); plastic cooling fan assembly; flywheel shroud; solid state ignition coil w/mounting screws; plastic inner air baffle; cylinder head (cover) and cylinder (side) baffles (sheet metal). The only difference in these baffles is the M10, M12 and M14 all share the same baffles over the cylinder head and on the cylinder, and the M16 use different (larger) baffles. The Kohler points pushrod hole will also need to be plugged with a Briggs & Stratton points plunger plug. And when installing the bearing plate, the cam pin hole will need to be sealed with clear RTV silicone adhesive sealant because the Magnum bearing plate will not cover the hole. By the way - I've always preferred to use clear RTV silicone adhesive sealant for three reasons: Due to metal any warpage (which is unavoidable in most cases), gaskets don't always seal the irregularities and imperfections between mating surfaces, especially thin metal covers; being it's an adhesive, it bonds parts together, forming a leak-proof seal; and being it's clear, a thin bead of silicone makes for a clean and professional-looking repair job. It can't be easily seen or noticed between the parts.

FYI - Solid state ignition provides a more stable ignition timing than points ignition. The ignition timing for a K-series engine is less stable because the points operate off the camshaft, which has a tendency to "move around" a few thousandths of an inch while the engine is running, which effects the ignition timing. Flywheel-triggered ignition timing, such as the Magnum solid state ignition, is more stable because it operates off the crankshaft, which doesn't "move around" as much as the camshaft. One thing is lessened and another is gained with either ignition system. 

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Edited Saturday at 03:06 AM by Donleecampbell

[953 nut 59,086]

9 hours ago, Donleecampbell said:

I am going to try to rebuild a m12 in a 312-8. I thought about looking for another engine , but didnt know if they all had the same pto shaft size or were brand specific. I also was wondering if any of the engines in the wheelhorse 300, 400, 500 series would be a direct swap into my 312 ?  

9 hours ago, Donleecampbell said:

tractor for 50 bucks !!! it was beautiful. he started it up and it smoked and had no power. he explained it was tired.

 

For $ 50.00 you are off to a good start. If you have a good machine shop nearby that will bore a cylinder and turn a crank for a reasonable price that would be the way to go.      Buying a used engine from another Wheel Horse would work but you won't know how long the used engine will last. One of our members here rebuilds engines and you may want to check with @richmondred01 to see what he would charge or ifr he has one already rebuilt for sale.

[richmondred01 2,295]

1 hour ago, 953 nut said:

For $ 50.00 you are off to a good start. If you have a good machine shop nearby that will bore a cylinder and turn a crank for a reasonable price that would be the way to go.      Buying a used engine from another Wheel Horse would work but you won't know how long the used engine will last. One of our members here rebuilds engines and you may want to check with @richmondred01 to see what he would charge or ifr he has one already rebuilt for sale.

I can rebuild it for you. Buying a used engine is always a gamble. I’ll make it right.

PM me if interested. 

[wallfish 17,830]

Yes, an engine from a 300 or 400 series WH is a direct bolt on. M10, 12, 14 16.

If you go with an older K series engine, the electrical wiring and switch will need to be done to change it from the M series magneto ignition to the K series battery ignition

 

11 hours ago, Donleecampbell said:

he started it up and it smoked and had no power. he explained it was tired

What color smoke? A bunch of dark smoke would be flooding fuel and it wouldn't have any power. A mosquito sprayer with lots of white smoke is oil burning

Could it be something as simple as a blown head gasket or a blocked muffler robbing power? Only an inspection of the engine first will determine what needs to be done from a simple repair to a full blown rebuild.

 

 

[Donleecampbell 3]

2 hours ago, wallfish said:

Yes, an engine from a 300 or 400 series WH is a direct bolt on. M10, 12, 14 16.

If you go with an older K series engine, the electrical wiring and switch will need to be done to change it from the M series magneto ignition to the K series battery ignition

 

What color smoke? A bunch of dark smoke would be flooding fuel and it wouldn't have any power. A mosquito sprayer with lots of white smoke is oil burning

Could it be something as simple as a blown head gasket or a blocked muffler robbing power? Only an inspection of the engine first will determine what needs to be done from a simple repair to a full blown rebuild.

 

2 hours ago, wallfish said:

Definitely white , lol. it wont rev up past idle. it runs for about thirty seconds and quits. it will start up again and repeat. after about four times it wont start until you let it sit for awhile.

 

[wallfish 17,830]

1 hour ago, Donleecampbell said:

 

 

Starving for fuel is my guess.

water in the bowl, dirty carb or both.

Old gas, clogged tank air vent, bad fuel line, clog in tank screen to fuel line, clogged fuel filter

 

Use a can of carb cleaner to spray directly into the carb while hand throttling the carb and it should speed up above idle. It won't run smoothly doing that but it'll show whether it's a fuel issue or not.

Do NOT use starting fluid

[Donleecampbell 3]

On 6/7/2025 at 9:39 AM, wallfish said:

Yes, an engine from a 300 or 400 series WH is a direct bolt on. M10, 12, 14 16.

If you go with an older K series engine, the electrical wiring and switch will need to be done to change it from the M series magneto ignition to the K series battery ignition

 

What color smoke? A bunch of dark smoke would be flooding fuel and it wouldn't have any power. A mosquito sprayer with lots of white smoke is oil burning

Could it be something as simple as a blown head gasket or a blocked muffler robbing power? Only an inspection of the engine first will determine what needs to be done from a simple repair to a full blown rebuild.

pulled the head....blown head gasket !! good call.

 

 

 

[richmondred01 2,295]

I’ve got two fully rebuilt 16’s ready to go.

PM me if interested.

[wallfish 17,830]

2 hours ago, Donleecampbell said:

pulled the head....blown head gasket !! good call.

Let's see where it's at afterwards but glad you found it could just be something simple as that