Magnum vs K series differences

[meadowfield 2,754]

I think it will, but just checking... will a k321 crank fit a magnum 16? assuming the main difference is the flywheel and magneto setup...

 

I've a k321 with no ancillaries and a stripped flywheel - and a Magnum 16 that needs a new crank... assume the rod and pin will fit the M16 piston? 

 

 

[953 nut 60,019]

I have never had them apart side by side but there has been a lot said about balance gears being required for the Magnum while they could be removed from the K Series. Perhaps @richmondred01 can tell us.

[meadowfield 2,754]

thanks, I already removed the balance gears from the Magnum when I replaced the piston. However after rebuilding with a fresh rod, It knocked worse than before I started (should've got an engine shop to check the journals)

 

I might just bite the bullet and split them both - 95% sure they are all the same internals

[953 nut 60,019]

56 minutes ago, meadowfield said:

split them both - 95% sure they are all the same internals

Seeing is believing.  Here is some information from Brian Miller's site about balancing an engine.

http://gardentractorpullingtips.com/balance.htm

K-series VS Magnum Crankshafts -

A K-series K301 crankshaft cannot be used with a K321, K341 or K361 piston/rings assembly without adding a lot of weight to the counterweights because the K301 crankshaft is balanced too light. The opposite would need to be done if a K321, K341 and K361 crankshaft is used with a K301 piston/rings assembly, or the engine would vibrate more than normal. If a K-series K301 crankshaft is going to be used in a K321, K341 or K361 piston assembly, it would need to precision spin-balanced.

The Magnum crankshafts are interchangeable with the older K-series crankshafts.... but the K301/M12, K321/M14 and K341/M16 Magnum crankshafts are all basically balanced the same... for a K301 piston/rings assembly. Some Magnum engines use three counterbalance gears. Just like the K-series, the two balance gears on the side of the block are to reduce the side-thrust of the counterweights of the crankshaft. But the lower balance gear in the Magnum is used to balance the rotating assembly because the Magnum counterweights are too light for the K321/M14 or K341/M16 piston/rings assemblies. Go here to learn how to align the three balance gears: Kohler Three Gear Balance Gear System Service Bulletin 208.pdf. (require Adobe Acrobat Reader and use Google Chrome web browser for a faster download of web sites with large files.)

For the heavier M14 and M16 Mahle piston/rings assemblies, the bottom balance gear simulates additional weight on the counterweights of the crankshaft so the engine will run with less vibration. If the Magnum balance gears are left out with any model, the engine will vibrate terribly! But if the balance gears are purposely left out, such as for high RPM operation, the rotating assembly would need to be precision balanced to reduce dangerous vibration. The older K-series engines will not vibrate more than it did before without balance gears installed.

And if a Magnum crankshaft is replaced with a K-series crankshaft, the Magnum balance gears shouldn't be used with the K-series crankshaft. If they are used, the engine may vibrate a lot.

If a Magnum (M12, M14 or M16) crankshaft require three balance gears, it can be used without the balance gears in a K-series block if it is precision spin-balanced to reduce the vibration (with the connecting rod and piston/rings assembly) on a crankshaft balancing machine.

And I have no idea why Kohler changed the crankshaft balancing with the Magnum single cylinder engines to a three balance gear balancing system. It make no sense at all to me. I mean, the way the older K-series engines was balanced worked great. But anyway, it'll be best to leave out the balance gears and have the rotating assembly (crankshaft, piston/rod assembly) dynamically and precision spin-balanced. By having this done, the engine, with no doubt, should run much smoother and possibly last longer.

The early K-series crankshafts have a 3/16" wide slotted [flywheel] keyway and a 5/8" diameter threaded stud w/nut to retain the flywheel, and the later K-series and all Magnum crankshafts have a #5 Woodruff [flywheel] keyway and a 3/8" bolt to retain the flywheel.

Edited May 27, 2020 by 953 nut