Kohler 321-341 upgrade possible?

[MilanWH 26]

I was wondering what the difference between a Kohler k341 and k321 is. Can a k321 be converted with just a carb/cam swap? Is there/stroke the same? Are the carbs interchangeable? Is the only difference between the magnum/non magnum the switch to an electronic ignition, eliminating the points/condenser? I know, a lot of questions, but I have a chance to get a 14 magnum with a broken rod and wonder if it would be possible to build it as a 16hp.

 

 

 

[JAinVA 4,619]

K341 and K321 have same stoke but 341 has a bigger bore. The heads on 10,12 and 14 horse engines have 9 bolts and the 16 horse has 10. You can covert a K to an M but the aluminum bearing plate needs to be changed out to mount the ignition module.

Edited October 24, 2022 by JAinVA

[MilanWH 26]

Excellent info JAinVA! Just what I needed. What about the carbs? 14hp-16hp the same or do they have different jets/bores?

 

[953 nut 51,797]

Here is information from Brian Miller's web site.

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 motor 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.

 

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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 clear RTV silicone adhesive sealant 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. [Return To Previous Paragraph, Section or Website]

[MilanWH 26]

953 nut, I apologize for not taking the time to find that complete, comprehensive info. Everything I needed already on this wonderful site. I'm having a lot of fun with a new to me 520hc that has a Kohler k341 swap that seems to run great. I found a 314-8 with a broken rod I've considered picking up because it has a nice 48" deck, the one I have is not in great condition. It's nice to know what parts are interchangeable on these engines.

Do you know if the k341 can drive a 60" deck? One of those is close to me for reasonable, if it isn't too rusty I might try that.

[Gardy22 0]

60 inch deck, I would prefer more power. But, I've heard a lot of problems with the 60 in. I've always used 48 in.

[peter lena 8,072]

@Gardy22  biggest problem with decks is neglect , and  no grunge breaking drying cleaning cycle. usually packed with wet rotting grass , improper spindle grease, (  if ever )  collective  drag  on mule drive eats pto clutch , that entire  set up requires a functional , detailing and upgraded lubrication to work as it should . this is only my opinion  and experience , none of my decks have issues , or  rotting going on . believe it or not , your pto lever can be very smooth and your deck can spin up without squealing / smoking effort . pete   

[Stumpjumper1946 0]

Wow, there is a wealth of information on this page.
Many thanks.
I now wonder if the "magnum" version has more power than the standard with ignition points?
Except for the electronic ignition and add on external shields I see no major difference.

I did a lot of reading when my K321 quit running and landed on this page by accident.
The pin that pushes the points moves freely but no longer moves when turning the engine so it appears something inside has broken.
There was no noise when I shut it off, but it now has no spark. It still blows air through the spark plug hole so it is a bit of a mystery.

From reading here, it appears I will have to pull that engine and dig into it.

The K series of engines are used in many different brands of garden tractors.
A friend has John Deere with them, another has it in a Farmall. At a yard sale there was a tractor with no identifiable markings that had a K341 engine. The controls suggested a Craftsman as they were similar to a third friends Craftsman.
So, we who intend to preserve these amazing engines have a vast network of info and parts to draw from. That is, if we are willing to trust, "the other guys who don't wear Wheel Horse red".