Decarboning M12 & M14

[Fordiesel69 233]

Ok, per the kohler K series manual, as well as the magnum manual, they suggest a 500 hr interval to decarbon.  The M12 has 534 hrs, and the M14 has 255 hrs.  As you can see even at 255 hrs there is a significant carbon ridge that will be eating up the piston in the not so distant future.  Good news is at least both of these engines have the style D mahle pistons.  That was the real reason I pulled the heads.  The suspense was killing me.

 

M12 Before:

 

 

 

 

M12 After:

 

 

 

 

M14 Before:

 

 

 

 

M14 After:

 

 

 

Edited October 8, 2013 by Fordiesel69

[wrightorchid 261]

What is the best way to do this?  Is there anything that can be done to prevent this buildup?   

[Wheel-N-It 2,967]

Yes, about every 100 hours spray 8oz of type 3 dexron atf into the carburator with the engine running at about 3/4 throttle. Don't choke the engine all the way down or hydro lock it, just use good common sense with the application. The atf has cleaners in it that eat away the carbon build up.

[Fordiesel69 233]

The (only) way to do this is to remove the head.  If you use additives to dissolve the carbon, it will just jam it down deeper into the rings.

 

Here is how I did it:

1.  Remove head, move piston to the lowest position.  BDC

2.  Tape around the edge of the piston to the cylinder wall using masking tap.  This keeps the carbon from getting stuck down inside

3.   Clean the valves, and cylinder deck with a plastic scaper, and if you are gentle, use a small razor blade.  Do not scratch any metal. 

4.  Use a razor blade to clean the carbon from the ridge at the top of the cylinder.

5.  Use a small precision screw driver to clear out around the valves.

6.  Finish off with a small brass brush.

7.  Remove tape from piston, smear a nice amount of grease low in the cylinder bore.  Move piston to TDC and wipe off the grease. 

8.  Use a razor blade and gently scrape piston top without putting scratches in it.

9.  Move piston downward very slowly and only enough to expose the grease, wipe the grease and carbon off the cynlinder wall.  Repeat this 1/2" at a time, or only enough to expose more grease / carbon.  By the time you get all the way to BDC, it should all be gone.  You should have wiped the cylinder a minumum of 5 times.  You will see what I am talking about.  Each time you move it down, more greae and carbon will be on the cylinder.

10.  Torque head per the book with a new gasket, but add this step........after a few hours & heat cool cycles, retorque the head once more to be sure.

[WH nut 553]

Looks like both motors are using a bit of oil.

[Fordiesel69 233]

The M12 I have put 19 hrs since the oil change, it has not burned a drop.

 

The M14 I have put 4 hrs and worked it VERY hard, and it has not used any (fingers crossed).  Only owned it for a few weeks.

 

All my K181's use oil, and seem to have more wet / shiney deposits rather than hard carbon crust.