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LT12H resto and re-build


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#31 Gabriel OFFLINE  

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Posted April 22, 2015 - 10:50 PM

Looks good!



#32 KennyP ONLINE  

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Posted April 23, 2015 - 06:23 AM

Did you get the ignition switch figured out?



#33 aevansgatech OFFLINE  

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Posted April 23, 2015 - 06:27 AM

I put the LT on hold for a bit until I get the deck finished, but I did end up ordering the proper replacement switch from Messicks along with a solenoid. Should be able to keep diagnosing the issue this weekend if the parts arrive
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#34 Tennblue59 OFFLINE  

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Posted April 24, 2015 - 10:09 AM

On the ignition switch - there are basically 2 kinds of switches, one for a magneto ignition, and one for a points/battery ignition. They are NOT interchangeable, and putting the wrong switch on a magneto ignition can fry the coil!
Once you know which type you need, you can pick a cheap "universal" one up at most places for about $15.00.

Remember that you probably have safety cutout switches in your ignition circuit - have to have your butt in the seat/foot on the brake/pto disengaged/etc, before the starter will engage. They are usually in series, so if any one is bad, no start! Trace through each cutout and make sure it is good. As a TEST STEP ONLY, you can run a jumper around all the safety switches to test the ignition, but I won't recommend you leave it that way once you are done testing...

As to the "hard turning" problem, you might want to open the engine up and see if the crank/con rod have seized. Low oil/dirty oil/no oil running often overheat this bearing and the rod melts aluminum onto the crank journal. Sometimes not enough to seize it tight, but just make it really hard to turn. This is in the top 1 or 2 reasons these engines fail. If not too bad, you can polish the crank and put in a new rod. But if it has seized and you keep running it, it WILL break and might toast the engine in the process. You have to pull the engine to inspect, but all you have to replace is the case gasket if everything is ok. Unscrew the cap off the rod and check the wear surfaces.

Best of luck!

#35 aevansgatech OFFLINE  

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Posted May 01, 2015 - 11:19 AM

So I got the new switch and starter solenoid. Went to replace the solenoid and noticed something.

Here's the connections it had (original solenoid). Good cable from battery to large post, black wire with good 25A fuse goes to the ignition, large post to starter motor, and two small "clip" wires at the solenoid base.

ImageUploadedByTapatalk1430497061.167560.jpg

My question is I also found a wire coming from the PTO interlock switch that wasn't connected to anything. It's a black wire with a ring type end connector, but I don't know where to connect it. I'm thinking it's a loose ground wire and maybe that's part of my issue with not starting.

I can't find the manual specifically for the LT12H, and my YT has an electric PTO switch so it is different.

Edited by aevansgatech, May 01, 2015 - 06:40 PM.


#36 aevansgatech OFFLINE  

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Posted May 07, 2015 - 09:09 AM

Spent a lot of time working on the LT yesterday.

Re-built the carb with a B&S kit and I didn't see any real issues there. Some of the tips were 'ridged' so I replaced them and the float had some minor debts but I didn't see any cracks

Got the new switch and solenoid hooked up, and will bench test all the way to the starter soon.

I also mostly pulled the engine out, but can't get the main pulley off. I'll give it another go this weekend

ImageUploadedByTapatalk1431007775.081054.jpg

ImageUploadedByTapatalk1431007785.559917.jpg
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#37 aevansgatech OFFLINE  

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Posted May 10, 2015 - 02:02 PM

Opened up the engine and honestly it looks good to me. I don't see any cracks, broken parts, metal shavings or anything like that

ImageUploadedByTapatalk1431284481.861421.jpg

ImageUploadedByTapatalk1431284495.627353.jpg

ImageUploadedByTapatalk1431284504.177454.jpg

I'm soaking the piston and valves in marvel mystery oil now and I'm kind of hoping just cleaning it out will loosen it up.

As a bonus I confirmed my starter circuit works now with the new key switch and solenoid!
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#38 aevansgatech OFFLINE  

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Posted May 10, 2015 - 02:05 PM

This little half moon piece did fall out loosely, though. Any idea where it could come from? My best guess is from the back of the piston head / top of the connecting rod based on where it fell from


Edited by aevansgatech, May 10, 2015 - 02:05 PM.


#39 Gabriel OFFLINE  

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Posted May 12, 2015 - 09:16 AM

This little half moon piece did fall out loosely, though. Any idea where it could come from? My best guess is from the back of the piston head / top of the connecting rod based on where it fell from

attachicon.gifImageUploadedByTapatalk1431284748.171035.jpg

Is the crankshaft gear removable? If so, could the half moon piece be the key for your crankshaft gear?


Edited by Gabriel, May 12, 2015 - 09:18 AM.


#40 aevansgatech OFFLINE  

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Posted May 12, 2015 - 03:09 PM

Is the crankshaft gear removable? If so, could the half moon piece be the key for your crankshaft gear?


I think so.. The larger gear is a solid piece with the camshaft, but the smaller timing gear is remove able off of the crankshaft

ImageUploadedByTapatalk1431461277.449740.jpg

I found a dimple on the timing gear and there's a dimple mark on the cam gear which I assume line up. There's also a hole in the cam gear which I'm not sure what it's for. I'll snap a pic when I can
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#41 aevansgatech OFFLINE  

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Posted May 13, 2015 - 08:39 AM

So with the crankshaft and piston out, it's still a bit difficult to turn. The only things in there are the valves (but no camshaft or tappets) and the flywheel

I'm thinking there's some restriction in the flywheel mounting, but looking at the parts diagram I just see a plastic bushing. Shouldn't there be a bearing as well? I'd like to have an idea how the flywheel is mounted before tearing it apart

#42 Gabriel OFFLINE  

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Posted May 13, 2015 - 08:54 AM

So with the crankshaft and piston out, it's still a bit difficult to turn. The only things in there are the valves (but no camshaft or tappets) and the flywheel

I'm thinking there's some restriction in the flywheel mounting, but looking at the parts diagram I just see a plastic bushing. Shouldn't there be a bearing as well? I'd like to have an idea how the flywheel is mounted before tearing it apart

There should be a bearing in the flywheel side of the block. It should have a replaceable one, or, the "bearing", may actually be the block itself.



#43 Gabriel OFFLINE  

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Posted May 13, 2015 - 09:03 AM

What's your engine's model number?



#44 aevansgatech OFFLINE  

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Posted May 13, 2015 - 10:39 AM

281707

The parts lists I found don't list the bearing separately, but it must be in the block
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#45 Gabriel OFFLINE  

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Posted May 16, 2015 - 09:37 AM

281707

The parts lists I found don't list the bearing separately, but it must be in the block

The parts diagram for your engine shown at jack'ssmallengines.com, shows that it has a replaceable bushing. Here's a link to the diagram: http://www.jackssmal...n/161975/114073 It's #2 in the diagram.






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