This 1969 Suburban 12  looks like it was stored inside earlier in its life. The paint is in pretty good condition. All the little parts, like the
belt guard, front frame cover, and starter belt cover are there. The front grille near the headlights is broken. Also, the connecting rod is
history. The crank will spin most of the way around, until a solid "thunk" can be heard. Plus, the piston does not move when spinning
the crank. The story about the final minutes of the tractor's operation was that the owner was mowing, when the engine "started
making noise, then just stopped". The tractor sat where it stopped, until rescued by a concerned Sears collector. Let's take this one
apart and restore it!
What happened to the connecting rod?
I always like trying to figure out a mystery, (after all, I am [was] a cop) so I spent a little extra time playing around with this engine to
see what happened to it. I really didn't have to, because I have another 12 hp Tecumseh with low hours just waiting to be painted and
bolted on. Something I liked about this tractor is that it came with the original type, oval muffler with the exhaust openings in both ends.
The first thing I did was to remove the muffler for transplant onto the other engine. I couldn't help but notice that something was
rattling around inside the muffler, so I shook it around and guess what came out?  Several small screws used to hold the throttle plate
onto the throttle shaft.
OK, so if the screws that hold the throttle plate on are in the muffler, then what's
holding the throttle plate on?  Better check the carb to find out. Surprise, surprise! The
throttle plate is missing!  Plus, the choke plate is about to get sucked into the engine
too, as it is only being held on by one loose screw. I didn't have to look too far to find
the throttle plate; it was stuck in the intake port. It had been floating around in there
for a little while too, judging by the way it got hammered by the valve. HOW COULD
THIS ENGINE RUN WITHOUT THE THROTTLE PLATE???  If anyone has any
ideas, let me know. I would later find that there were two other screws under the
cylinder head. One was pushed into the soft aluminum material. I had to back it out to
remove it. All right, so now I have five screws floating around inside this engine, but
only three are missing from the carb. The only thing I can figure is that two (or more)
came loose previously and were replaced. The moral of the story is to make sure your
screws are tight. Use Loctite, or other thread locking solution to keep them where they
belong.
Well, the throttle thing had me a little stumped. Let's move on. The next thing was the
blower housing. After taking the belt guard off, I noticed that the screen that should be
on the flywheel was missing. Shiny, new bolts were holding the starter belt pulley onto
the flywheel, but the screen was nowhere to be found. Not good news if the tractor
was being used  to mow with. The screens are there to keep clippings and other things
from getting sucked into the cooling system. Don't forget that these engines are cooled
by massive amounts of air passing over the cooling fins. If you have any doubt about
how much air is forced through the engine, hold your hand about two feet from the
right side of the engine as it is running at full speed. Anyway, when I finally got the
blower housing off, it was obvious that this engine could not have been cooled
effectively. There was all kinds of debris blocking the path of the cooling air. I thought
at first maybe a mouse had made a nest in there, but as I picked through it I found it
was just junk that would have been blocked by the screen if it were there. I'm sure
this engine was overheating in its final minutes of operation.
click photo to enlarge
click photo to enlarge
click photo to enlarge
click photo to enlarge
Those two pieces of
the key are only
supposed to be one
piece.
click photo to enlarge
Onto the flywheel...It came off with minimal effort (and a large puller). Of course the
key was sheared. Any time the engine comes to an abrupt stop, as this engine
obviously did, the key will shear. This is intended to keep the kinetic energy of the
flywheel from twisting the crankshaft. It's the sacrificial lamb, so to speak. No
problem here, they are cheap to replace. Now that the engine is nearing a stage where
I can remove it from the frame, I thought I would drain the oil so it didn't leak all
over the floor of the garage when I tipped the engine. Here's the biggest
surprise...THE ENGINE HAD NO OIL!  What you see in the bottom of the coffee
can on the right is all the oil that was in the engine. So on top of the fact that the
engine ate at least five screws and had no way to cool itself, it also had no refined
dinosaur in the crankcase! No wonder it was in self-destruct mode. How many of us
get new equipment and look at the first couple of pages of the manual where it has all
the generic "warning" and "caution" statements, and chuckle to ourselves about the
rudimentary statements made by the writer. "Make sure the oil level is within
acceptable range", is a common sentence.  Gimme a break, I've often thought to
myself, who would operate an engine without checking the oil??? I guess the previous
owner of this tractor did. He also didn't change it often, judging by its jet-black color.
With any luck, I'll just get away with an overbore, piston/rings and a new connecting
rod when I decide to rebuild this engine. I'm not optimistic though. I suspect that the
crank and cam will be just a scored as the cylinder walls.
click photo to enlarge
2/22/2001, I finally got the time to tear down the engine all the way. The rod is a
sad sight. I don't know if the crank can be used again either, as there is a
considerable amount of metal tear-out. The skirt on the piston is broken where the
rod hit it. The valve gears seems to have survived the oil free operation unharmed.
The bore is within acceptable range. There is a little scoring where the piston skirt
dug in. It will clean up. I bet this thing sounded like the hammers of hell just before
it "quit."  I'll never understand how someone can do this to a perfectly good piece of
equipment.
click photo to enlarge
click photo to enlarge
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