M18 Teardown

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Well-known member
Jul 19, 2010
Farmville, North Carolina
Jeremiah Chamberlin
More Teardown Pics:

Pic 24 A shot of Rod #2 on the crank.


Pic 25 Close-up of the same shot.


If you can’t tell from the picture, not only did the weight from the governor make an impression on the aluminum of the rod cap, but it also sheared off part of the stud before twisting off the other side making a second mark on the aluminum. The upshot of all this damage was that the nut did not turn on the stud; instead, the stud turned in the rod. The full extent of the damage was not evident until the internal dimensions of the rod end were measured.

Pic 26 Rod #1 internals.


In the picture above, please note the designation of this rod as Rod #1, this mark is INCORRECT. Evidently, I got the crank turned around and started counting from the PTO end instead of the Flywheel end. In any case, the designation is obviously in error, since the photo above clearly shows the cam gear and the “E” on the crank shaft. I’m assuming that I numbered the jugs and the pistons correctly –I hope!

Pic 27 Another shot of the “big end” of Rod #2.


Pic 28 Another shot of the same subject from a different angle


The series continues with shots of either side of each piston.

Pic 29 Piston #1 (Top side?)


The Kohler manual cautions against using metal punches and scribes to mark parts; I respectfully disagree. I scratched ID marks on most parts with a scribe, and if I hadn’t I would have gotten things even more mixed up than I did.

Pic 30 Obverse of Piston #1



Pic 31 Piston #2 (Top?)


Pic 32 Obverse of Piston #2 (Bottom?)


I failed to document much about the disassembly of the valve train, but I thought I would include a shot of the tool I used, procured from my local NAPA store which also deals with Briggs & Stratton engines. I picked up the tool when I was working on the 16 HP twin B&S motor similar to those installed originally in IH Model 582 among others. A standard valve spring tool can also be used on a Kohler “jug” from what I understand.

Pic 33 B&S Valve Tool


When I was done getting the valves disassembled, I decided to put all the relevant parts together in a baggie together with a tag clearly indicating which valve, tappet, spring, keeper and seal went together.

Pic 34 Exhaust Valve #1 bagged and tagged.


Note: The last two images were taken with my camera set to VGA mode: 640 x 480 –it is the only format which comes close to the 100K limit set by this forum; any higher setting requires re-sizing of the photograph before posting; and even some of the VGA shots have to be cropped to get under the 100K limit. (I’m not complaining, I’m simply trying to pass on some tips and explain why the last two images appear smaller, or at least the do in the application in which I’m editing this document.

This post/thread will have a follow-up concerning the Inspection of the parts to determine what will need to be replaced or reworked. The purpose of this post/thread is simply to share the raw data of what things looked like before they were cleaned up and to confirm the full extent of the damage documented in the “M18 Starting Problem” post.


Well-known member
Jul 19, 2010
Farmville, North Carolina
Jeremiah Chamberlin
The reason we’re tearing into this engine is because of the damage caused by the governor’s self destruction. Some light smoking was observed and oil seeping noted. The damage was caused by a combination of (1) overheating (according to Kohler) and (2) the fact that the Service Bulletin 246 date 4/98 for Kohler engines KT17, KT19, M18, M20, and MV16-20.

For Troubleshooting history on this engine, see IH Cub Cadet Forum CCC and MTD Machines & Equipment M18 Starting Problems at HERE for details.

Pic 0 Damage to crank case as viewed from the outside.


Pic 01 Motor on Lift.


Pic 02 Motor on bench.


Pic 03 Spec ID tag


Engine Identification: Magnum 18 HP (M18) Spec# 24646
(One of three used in Cub Cadets, compare Spec# M18-24506 and M18-24647)
From Service Manual appears to be Later Version (30 Deg Valves) >= S/N 1816500656, p. 1.9 Section 1, Specs; cf. text Section 10 p. 10.4 which gives the break at >= S/N 1917809296 (?).
Note: Identification courtesy of Jim Diederichs, see post called out above

Upon breaking the motor apart, I discovered two matching numbers inscribed by hand on each side of the block underneath the closure plate. In the case of the 1862 motor, it was inscribed “2459” which I thought was a spec number, but it is one digit too short, a Kohler spec number is five digits long and the mark has only four digits. I don’t think the block had ever been apart before, so I’m thinking the marks came from the factory.

Pic 04 Block inscribed under Closure Plate (Marked Up)


The purpose of this teardown is to determine how much work (and how much money) it will take to return the engine to service. The governor self-destructed and took out the crankcase on its way down. A new crankcase has been procured; and it came with the governor intact. I will document the teardown and then, after cleaning, document the inspection.

To keep track of all the components, it is necessary to orient them in the engine by Side:
• The Sides are called out in Fig 9-12 of the Service Manual, Disassembly chapter, on p. 9.4.
• Cylinder/Side #1 toward the Flywheel (for Kohler the Flywheel is at the Front).
• The breather is on Side #1; to the left as you face the PTO, to the right from the Flywheel.
• The governor, the oil pump, and the oil filter are all on Side #1

I proceeded to tear the motor down, and I will let the pictures do the talking, as most of them should be self-explanatory.

Pic 05 Flywheel ready to pull


Pic 06 Flywheel off.


Pic 07 Barrel for and piston for Side #1


Pic 08 Piston #1


Pic 09 Barrel and Piston for Side #2


Pic 10 Piston #2


Pic 11 Bottom of Bore on Side #1


Pic 12 Whole of Bore for Piston #1, as seen from the bottom


Pic 13 Top of Bore for Side #1


Pic 14 Whole of Bore #1 as seen from the Top


Pic 15 Bottom of Bore for Side #2


Pic 16 Whole of Bore #2 as seen from the bottom


Pic 17 Top of Bore #2


I was finally able to split the crank case, after searching for the several bolts that hold it together.

Pic 18 Crankcase split in half (Side #1 removed)


I found the decimated governor gear in the bottom of the crankcase, with several of the smaller pieces tightly grouped around the oil pump intake screen.

Pic 19 Governor Gears


The full extent of the damage done to the Side #1 was also evident.

Pic 20 Side #1 Internal Shot 01


Pic 21 The same area of side #1 as seen from a different angle.


Once it was open, I could see what happened to the governor gear.

Pic 22 The “Scene of the Crime” showing all three components involved in the “collision” between the up-swinging rod cap #2, the governor weight involved in the accident (notice the marks on the side, the other weight was “clean”), and the #1 side of the case which graciously gave way preventing further damage.


Pic 23 Also, with the “jug” out of the way, the crack that was originally perceived as limited could be seen to be more extensive than first supposed. (It may not show up well in the picture, but the crack along the jug hole was evident on the outside as well as the inside.)



Well-known member
IHCC Supporter
Dec 21, 2007
Aaron Schmidt - Xtreme Motorworks
Nice write up, thanks! I have torn apart a few of these engines and usually when they let go, seems like i am left with junk...


Well-known member
Jul 19, 2010
Farmville, North Carolina
Jeremiah Chamberlin
Thanks, Aaron. I am responding to a request from Art Aytay. I'm hoping this one won't wind up being junk, but it all may depend on parts availability.

The link to the history of diagnosis on this engine, which I forgot to edit after pasting in my copy, is corrected HERE.

Also, I meant to say that Service Bulletin #246 dated 4/98 for Kohler engines KT17, KT19, M18, M20, and MV16-20 that Jim Diederich brought to everyone's attention <u>was not performed</u> on this engine.