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LT12H resto and re-build


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#1 aevansgatech OFFLINE  

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Posted March 27, 2015 - 07:39 AM

Hey guys,

 

Got an LT12H with an unknown engine problem. I'll detail the rebuild process here and hopefully learn some new tricks.
 

Pardon my silly questions :wave:

 

 

First up, I've got it jacked up off the ground for easier access to remove the deck and keep the damaged front left tire off the ground. Step one is hijacking the good seat and mower deck from the 12H and putting it on my 16H.

 

As far as the engine goes, I'm not sure where to start. I'd like to be able to tell if the engine turns or is seized up before removing it completely. Can I just turn the lower pulley with the transmission disengaged?

 

Here's the starting point:

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#2 KennyP ONLINE  

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Posted March 27, 2015 - 08:37 AM

You should be able to turn the lower pullies if it's not locked up.


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#3 boyscout862 OFFLINE  

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Posted March 27, 2015 - 08:38 AM

Yes but, disengage the sparkplug wire and ground it first. There is allways the possibility of the engine kicking when turning by hand. Get in the habit of pulling the sparkplug wire off whenever playing with small engines. That is an easy engine to work on and replacements are plentifull. Download the Repairmans' Manual from our manuals section. Good Luck, Rick


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#4 KennyP ONLINE  

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Posted March 27, 2015 - 08:44 AM

Might just pull the plug, making it easier to turn over.


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#5 aevansgatech OFFLINE  

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Posted March 27, 2015 - 09:39 AM

Great! I'm hoping for some tolerable weather this weekend to be out in the garage



#6 Texas Deere and Horse OFFLINE  

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Posted March 27, 2015 - 11:28 AM

You could remove the main drive belt and see if you can get it to run as just an engine.


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#7 aevansgatech OFFLINE  

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Posted March 27, 2015 - 07:09 PM

Ok so I can turn the engine but barely with my hands on the pulley.

Before I go through the rest of the checks (spark plug, starter, etc) just how difficult should it be to turn the 1 cyl engine by hand? Trans is disengaged but main drive belt is connected

#8 KennyP ONLINE  

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Posted March 27, 2015 - 07:15 PM

I would think easier than that. Is the  spark plug still in it?



#9 aevansgatech OFFLINE  

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Posted March 27, 2015 - 07:58 PM

With the plug out its a bit easier but I still have to put some effort into turning the lower pulley

More effort than turning the 16 horse for sure so there's something gummed up inside the head

Here's the plug.. Pitch black

ImageUploadedByTapatalk1427504324.150184.jpg ImageUploadedByTapatalk1427504332.413278.jpg

The piston isn't completely stuck so has anyone had luck using Gumout, a penetrating oil, or an additive to free up the valves/piston while turning it?

Edited by aevansgatech, March 27, 2015 - 08:08 PM.


#10 Bill 76 OFFLINE  

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Posted March 27, 2015 - 08:51 PM

 Put some Marvel mystery oil in the plug hole and turn it a few times to spread it around and let it soak that should help free things up--Atf also works good to free up old crud.



#11 glgrumpy OFFLINE  

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Posted March 27, 2015 - 09:16 PM

Belts can rust into pulleys, even partially and hold pretty tight. Starter motors can have drives stick engaged and you're turning it also, binding some.
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#12 aevansgatech OFFLINE  

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Posted March 27, 2015 - 10:33 PM

Had a great night wrenching in the garage

Drained the oil and old gas for starters, had the battery tested and charged, removed the gas tank, replaced the rotted fuel line and added a new filter and shutoff valve, and removed the spark plug.

ImageUploadedByTapatalk1427513421.535858.jpg
ImageUploadedByTapatalk1427513432.499645.jpg

I'm torn whether to try freeing it up still mounted or to take the whole engine out to play with. I'm thinking its worth replacing a few main gaskets, and possibly doing a carb rebuild for a learning exercise.
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#13 Texas Deere and Horse OFFLINE  

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Posted March 27, 2015 - 10:38 PM

I would at least pull the head and see how the bore looks and also see how bad the carbon buildup is before pulling it off the tractor and doing a complete rebuild. It may just need to be soaked up good and run for a while to get all the crud out of it. Also do a couple 3 oil changes back to back if it runs good.


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#14 aevansgatech OFFLINE  

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Posted March 28, 2015 - 12:43 PM

Pulled the head off this morning and I think it's good news

There's a ton of carbon buildup, but I don't see any real damage on the piston, inside the bore, or to the valves/seats

ImageUploadedByTapatalk1427564533.155860.jpg

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The head gasket looks pretty bad so I'm going to replace it

ImageUploadedByTapatalk1427564586.875852.jpg


Best chemical to remove the carbon?

Will the marvel mystery oil really take care of all that?
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#15 aevansgatech OFFLINE  

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Posted March 28, 2015 - 05:16 PM

Cleaned up the head as best I could. I made sure not to scratch into the metal itself but I couldn't get all the deposits off

ImageUploadedByTapatalk1427580843.070869.jpg


New head gasket installed and I'm going to at least see what happens when I try starting it with fresh fluids
ImageUploadedByTapatalk1427580904.342384.jpg
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