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Kohler Magnum 12 Hp Head Gasket Blown?


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7 replies to this topic

#1 esmarkey OFFLINE  

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Posted October 21, 2012 - 10:55 AM

Hi, new to the forum.

I've got a WHEELHORSE 312 8 speed with the Kohler Magnum 12hp that I bought used this past summer. My son is the one who uses it (constantly), and I noticed that it was making a very loud sound last time I heard him running it.
Today when he was trying to start it, it would not stay running but would try to start. Again, the loud noise was bothering me so I went out and took a look.
What I found was air leaking out just below the head and blowing on the muffler. We took off the cover and I found several of the head bolts loose.
I snugged them up using a criss cross pattern, but results are the same. Won't stay running, air leaking, and loud sound (can't explain)

I am not sure if I am using all the correct terminology, but am wondering if this is common? I also wonder if replacing the head gasket is something that can be done easily, and if replacing it will fix it? I did look fro cracks in the head, but did not see any.

Any help would be appriciated.
Thanks in advance,

Eric

                       

#2 KC9KAS OFFLINE  

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Posted October 21, 2012 - 11:22 AM

:welcometogttalk:
If you were able to get to the head bolts to tighten them, you should be able to replace the head gasket without any problems. Be sure to use a brand new head gasket, and use a torque wrench to tighten the bolts to the manufactures spec.

Oh, make sure the head isn't warped...
  • esmarkey said thank you

#3 esmarkey OFFLINE  

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Posted October 21, 2012 - 03:56 PM

Thanks KC9KAS, I doesn't look like a real tough job. I hadn't thought about a warped head...
I was surprised to see the bolts loose. Is this a common problem with the Kohler 12's?

anyone have a suggestion on the best place to order the head gasket?

#4 JDBrian OFFLINE  

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Posted October 21, 2012 - 05:11 PM

Also make sure you clean the carbon off of the head, piston and top deck while you have it apart. This is supposed to be done every 500hrs as routine maintenance. In particular make sure there is no hard carbon on the top of the cylinder deck and flatten the head on a piece of glass with wet paper. The hot exhaust leaking out through the gasket is bound to have left some deposits on the head and/or the top of the cylinder. You won't get a good seal unless you have 2 clean flat surfaces. Also, make sure you can get all the head bolts to thread in far enough to seat the gasket without any resistance. A bolt that is difficult to screw in will cause a false torque reading. Re torque after running the engine for 15 minutes. There is a specific sequence for tightening the bolts which can be found in the service manual. It's available from Kohlers web site. It's not a difficult job but you need to watch the details.
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#5 esmarkey OFFLINE  

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Posted October 21, 2012 - 07:34 PM

Thanks Brian, when you say "flatten" the head on a piece of glass" Do you mean to wet sand it with the paper on glass so it is flat?
If so, what grit works best?

#6 JDBrian OFFLINE  

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Posted October 22, 2012 - 05:04 AM

Thanks Brian, when you say "flatten" the head on a piece of glass" Do you mean to wet sand it with the paper on glass so it is flat?
If so, what grit works best?


Yes, that's what I meant. Make sure the glass is flat and not scratched. You could use other flat surfaces but glass is usually the easiest to find. Using a higher grit of like 400 will make the job go slow. I used 600 then 400 when I did a K321 head last year. It took a long time to get it flat but the results were good. After I did it I read that you can use a coarser paper like 200 or lower, as long as you are careful, then finish up with a fine grit. It also depends on how much you need to remove. My HG was leaking on the cylinder side so the head wasn't in really bad shape although the engine had been over heated by being run while the cooling fins were plugged up with grass clippings. I later discovered that the engine has a cracked block although it still runs pretty well. It just leaks some oil through the cylinder. I had to spend some time on the cylinder deck to get the hard carbon deposits off of the surface. Carbon tends to build up near the exhaust valve and can cause some problems if you don't remove it. The manual says to do this every 500 hrs but it almost never gets done until the engine comes apart for some other reason. I bought my Kohler parts from OPEEengines.com.

#7 LilysDad ONLINE  

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Posted October 22, 2012 - 06:48 AM

Perm-a-Tex has a Gasket Remover in a spray can. Spray it on the nasty Perm-a Tex and it foams up and disolves it.
Here's a little secret; it does the same thing with carbon deposits. Spray it on, leave it sit a little bit, and wipe carbon away.
  • KennyP said thank you

#8 Cvans OFFLINE  

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Posted October 22, 2012 - 07:11 AM

I purchased a really nice Cub Cadet 129 for $125.00. He thought it had a bent valve but as it turned out it had a bad head gasket. When I got it apart I found the head was badly warped and cracked. Cleaned things up, installed a used head and it runs like a clock. The rest of the advise you have received here is spot on. Good luck with your project.