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Sears St -12 Tractor

st -12 sears

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#1 Mike Unwin OFFLINE  

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Posted November 17, 2013 - 12:08 PM

Morning,

 I just got back with a Sears tractor it is a ST-12 tractor with snow blower,front push blade, rear lift hitch and one furrow plow, and the mower deck.It came with all manuals ,after reading here am I correct in thinking this is a Roper built unit ? I found the engine numbers 143 67012 serial 6316E so it seems to be a 14 horse Tecumseh engine a OH140 if I read this right.I went there to get another tractor a Waterloo and came back with both , one last question please where is the tractor info plate on this ST 12 ? Thanks Mike


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#2 TAHOE OFFLINE  

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Posted November 17, 2013 - 01:09 PM

Yes it is a Roper built tractor. I can not find those motor numbers, I know most parts interchange #'s have changed since back then.

If it is a OH14, then it is a replacement. The mid 70's ST12's were also overhead valve motors, they all look the same on the outside maybe its a 12. Look at the block at the front lower corner under carb right where it bolts to frame, should be a number stamped in oil pan, tells Hp of that motor.

The model plates were usually mounted under the front of the seat right behind shifter, but when Sears moved the gas tank under the seat in 75, the began riveting plate to firewall right behind motor.


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#3 MH81 ONLINE  

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Posted November 17, 2013 - 01:47 PM

I only found one reference for 143.670012 (one extra 0) it did show that as an OH14
If you try 143.672012 (2 instead of a 0) that is an OH12, either way there is a number missing. Would you mind checking the number again.
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#4 Mike Unwin OFFLINE  

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Posted November 17, 2013 - 02:41 PM

I took another look and found a tag in front of the seat it reads S1725039 looks like OC 3973 I will go back and see if I can find more numbers on the motor. So ST-12 meant 12 horse ?

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  • ST-12 tractor.jpg
  • ST-12 tractor b.jpg

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#5 TAHOE OFFLINE  

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Posted November 17, 2013 - 03:02 PM

Yes, ST 12 stand for 12 horse.

 

That number would be 917.25039 , is it maybe 917.25930? I cannot find any info for 25039.

25930 would make it a '76 model, along with the color scheme and plastic gas tank under seat.' 76 was last year for ST12 model also so I would almost be the farm it's '76 model.

As I said, check the block in front lower corner by flywheel, instant indicator of HP rating.


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#6 Mike Unwin OFFLINE  

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Posted November 17, 2013 - 03:28 PM

Okay you are correct it is a 12 HP and it is a 1976 going by the hand writing in the owners manual and the dates on the lower pages. So it should be the same engine as my 1969 Bolens 1220 tractor. The reason I got all this stuff for free is the ST -12 has no spark and the owner was told the module is very expensive so he said I could have all of it.If anyone needs a page from the tractor manual or implement manuals I can scan and post it. Thanks Everyone sorry about the tractor tag confusion it is really hard to make out. Cheers Mike


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#7 TAHOE OFFLINE  

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Posted November 17, 2013 - 07:02 PM

Nope not exactly that it's the same as your Bolens.

First pic is a '68 12 Hp Tecumseh, second pic is a '77 16 overhead Tec like your ST12 motor. While similar, they are different.

 

Also, these motors use a Solid state ignition module. He is correct, they are expensive to buy the original ones, but do not fear, there are several alternatives out there for replacement. Your Bolens most likely uses the first gen module the Sears will us the 3 rd gen one

* For a direct replacement, check out Dale Colvert's Overnight Solutions ignition, it is a modern day direct bolt on.

* Ed Stoller has a website www.enginesandmagnets.com   He explains the workings of the ignition system and he offers a new pickup sensor, you buy other parts that explains. His buddy Mike Brown sells a complete kit you can buy linked on his website. These systems convert ignition over to battery-auto coil.

* Brian Miller on garden tractor pulling tips also has a couple conversions, again these convert to battery ignition.

*My buddy designed another system for my tractor as I burnt up 2 modules in 1 month. Here is link to my write up.

http://gardentractor...ycoil-ignition/

 

 

68 SS 12 flat head 12 Hp Tecumseh

100_0477.jpg

 

77 16 Hp Over head Tec

100_0803.jpg


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#8 Mike Unwin OFFLINE  

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Posted November 17, 2013 - 09:26 PM

I will post a picture tomorrow when it is light,this ST-12 has a flat type head on the engine with a large horizontal muffler.Maybe mine is a early 1976 unit,when I have time I will scan and upload all the manuals. MMMMM snickers Cheers Mike

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  • engine.jpeg
  • cover.jpg


#9 Mike Unwin OFFLINE  

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Posted November 18, 2013 - 09:05 AM

This is the engine must be an early one then.

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#10 TAHOE OFFLINE  

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Posted November 18, 2013 - 09:49 AM

I very well could be wrong, I thought Sears switched all the Tec motors in the Suburbans over to overhead valves in '73.

Then I've only dealt with my 68 SS12 and my 16's so have not dealt with the later 12's.

 

The serial number shows it was made in 1976 on the 316th day so that maybe a late '76 tractor. I was kind of thinking it maybe '68 year, but the starter, dipstick and genereal appearence puts in in the 70's era so probably original. Guess I learn something new too!


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#11 DB-Suburban OFFLINE  

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Posted November 18, 2013 - 08:48 PM

in 1973 only the 14, 16hp tec engines are ohv 12hp is still flat head


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#12 Mike Unwin OFFLINE  

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Posted November 19, 2013 - 09:19 AM

When I first saw these tractors with the belt drive part out front I thought they were a Wheel Horse design later learned Roper. There is another chassis there I might see if it is available and make one from two.Thanks Mike



#13 Mike Unwin OFFLINE  

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Posted November 22, 2013 - 04:45 PM

I have uploaded the owners manual,3 point hitch manual and the snow blower manual in the Manual section,,,,, enjoy !


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