Terramite engine failure?

Ryan313

Tractorologist
Senior Member
Member
My buddy got a load, a large load of millings and I told him I would spread it. About an hour in, I shut it off to talk and it backfired. I slowed it down before shutting it off, but I have to admit not as much as I should have. It has never backfired, so I thought that was odd. I went to start it, and after half a turn it locked. I was able to turn it back some, and hit the key, same thing. This time, I could not get it to turn either way. I got the starter gear disengaged, so it is not the starter. I took the plugs out thinking maybe the needle valve got stuck and it hydrolocked, nothing. We wound up getting somebody else’s Kubota. I know one of the terramite engines is prone to blowing up... which one is it? I have the Kohler magnum 20. Any ideas?
 

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That seems like a design flaw, does that happen often? We’ve all seen a lot of engines backfire, and we’ve all seen engines shut off at very high rpm, but they don’t break rods? I hope tomorrow that I can get the engine out and see what happened.

Also, the Kubota is a nice machine! A slightly larger bucket and a bit of ballast would go a long way though. One thing I preferred about the terramite is the round bucket. The round bucket made it easy to put in float, and drive back and forth to get a decent finish.
 
The engine wasn’t too bad to remove, the only stubborn part was the coupler on the output shaft, which came off after some help from a pickle fork.
 

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What's the model # of this engine? If it's what I think it is and you need a crank, a vertical crank will fit. Just have to machine the PTO end to match yours!
 
Here's the Kohler crankshaft manual:
 

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Well I found the problem! I pulled the heads and pressed on the piston, one moved. I then took an air nozzle in the dipstick tube and popped the piston out.
 

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Did anything else get damaged?

Might be an easy fix!

I have one engine that still runs with a huge hole in the block. Threw the rod, and busted the block. Used 2 pieces of metal to sandwich over the large hole, JB weld, new rod and it runs like a new one. Well it did a decade ago, its been sitting on the shelf after I parted the tractor out to fix other tractors.
 
If the crank journal is still good, likely an easy fix. If the rod got into the lower end of the bore, just use a dremel and chamfer the edges down and that won't hurt a thing. If fixable, be sure to clean the oil sump screen, as I've seen some magnums toss rods due to the screen being clogged. The screen is on the small side to begin with. Does the rod half still on the crank rotate smooth? I figure the backfire broke the rod, and the rod journal is still fine.
 
I went out to lunch, and took the tractor with me to wash it. Since the engine was out, I had a good opportunity to clean out 40 years of oil leaks and spills.

I also looked closer at the cylinder walls, they don’t seem to be in the best shape. The engine burned a little oil, nothing horrific but enough to notice. I think I will likely have to bore the cylinders, I think it is beyond a hone. Do you guys think I should just full rebuild the engine at this point?
 

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