retiredvolunteer

[retiredvolunteer]

I am new @ posting, but I am getting desperate. I have a kohler Triad OHC TH-18 twin. cyl#1 seems to be fine;compression, spark and fuel burn. Cyl#2 has no compression and when I removed plug, piston is stuck in upper position does not move when engine rotated by hand and unburned fuel is apparent in the chamber. Also engine seems to run fine only on cyl#1 but is low on power. drained oil no metal filings. Replace coils and spark is good for both cylinders. How can this engine even run with no clanging and if cyl#2 piston is not moving?

 

[bertsmobile1]

The engine sounds like it is toast.
Apparently the sleeves can move down the cylinder then when the piston comes up the rings get caught on the sleeve.
So I was told by tose here who know better then me.

In any case your motor has a broken con rod minimum which will probably be terminals as most parts have been discontinued.

I have one here with good barrels but broken timing s[rockets which are NLA and I could not find any used any where.
There was a thread on mower wreckers a while back which those who contributed to will most likely direct you to.
But I can not get any parts of that series engine down here.

 

[ILENGINE]

I am new @ posting, but I am getting desperate. I have a kohler Triad OHC TH-18 twin. cyl#1 seems to be fine;compression, spark and fuel burn. Cyl#2 has no compression and when I removed plug, piston is stuck in upper position does not move when engine rotated by hand and unburned fuel is apparent in the chamber. Also engine seems to run fine only on cyl#1 but is low on power. drained oil no metal filings. Replace coils and spark is good for both cylinders. How can this engine even run with no clanging and if cyl#2 piston is not moving?

I suspect the sleeve moved down, the piston caught it, but instead of pulling the sleeve down, and taking out both rods, it just broke the rod at the crank journal, which clears the rotating parts of the engine. Like Bert said, you are basically done at this moment. There is most likely a Kohler Command conversion available if you want to spend the money and put in a new engine.

The Triad engine used what is called lost foam casting technology. the upper half of the crankcase, the intake manifold, and heads are molded as one piece. Because of this setup the cylinders had to be bored from the under side of the crankcase and then the sleeve pressed in. So when the cooling fins of this engine would get clogged with various foreign materials like grass, mouse nest, etc they would do the same thing that the briggs does to the valve guides in the heads when they overheat. The aluminum expands more than the cast iron and looses clamping tension and then they start moving.

 

[retiredvolunteer]

I suspect the sleeve moved down, the piston caught it, but instead of pulling the sleeve down, and taking out both rods, it just broke the rod at the crank journal, which clears the rotating parts of the engine. Like Bert said, you are basically done at this moment. There is most likely a Kohler Command conversion available if you want to spend the money and put in a new engine.

The Triad engine used what is called lost foam casting technology. the upper half of the crankcase, the intake manifold, and heads are molded as one piece. Because of this setup the cylinders had to be bored from the under side of the crankcase and then the sleeve pressed in. So when the cooling fins of this engine would get clogged with various foreign materials like grass, mouse nest, etc they would do the same thing that the briggs does to the valve guides in the heads when they overheat. The aluminum expands more than the cast iron and looses clamping tension and then they start moving.

Thank you for you input. I have seen short blocks for the Th-18 advertised on line. Could they solve the problem?

 

[reynoldston]

Seeing you can get by with the low power run it till it quits. Then replace the engine. It might even run for a long time yet??? Now what is this retied volunteer all about. It sure sounds like the something I am doing. Other then a few mowers and motorcycles I still repair in my shop I have been doing volunteer work. Right now I deliver home meal service to shut-in and take clients to doctor appointments that don't have a means to do so through the county services. Be surprised with the new people I meet.

 

[ILENGINE]

Thank you for you input. I have seen short blocks for the Th-18 advertised on line. Could they solve the problem?

I would assume those are used short blocks. Since certain parts have been obsolete for a few years now. the oil pump gear has a bad habit of wearing on the oil pump input shaft and cannot be replaced. Also the timing belt requires special tools to set the timing correctly when installing the belt, and well as requiring a certain preload before tightening down the adjuster.

 

[retiredvolunteer]

I suspect the sleeve moved down, the piston caught it, but instead of pulling the sleeve down, and taking out both rods, it just broke the rod at the crank journal, which clears the rotating parts of the engine. Like Bert said, you are basically done at this moment. There is most likely a Kohler Command conversion available if you want to spend the money and put in a new engine.

The Triad engine used what is called lost foam casting technology. the upper half of the crankcase, the intake manifold, and heads are molded as one piece. Because of this setup the cylinders had to be bored from the under side of the crankcase and then the sleeve pressed in. So when the cooling fins of this engine would get clogged with various foreign materials like grass, mouse nest, etc they would do the same thing that the briggs does to the valve guides in the heads when they overheat. The aluminum expands more than the cast iron and looses clamping tension and then they start moving.

Thank you all for your help. reynoldston; This motor is from a grasshopper riding mower from the school I volunteer for; doing electrical, computers, whatever to keep costs down. It takes up a lot of retirement time; but it is good to give back. You folks are doing good things with your free advice and I am sure it is appreciated.

 

[bertsmobile1]

Currently I am doing exactly the same job.
We bought a CH620 Kohler from SES for $1100 and when it gets here I will see what is needed to be done to do the swap.

You can fit and Kohler Horizontal shaft engine in there and if you stay with Kohler you can reuse the front pulley & flywheel.
Walkers are worth the effort of repowering as they are well made and will run for a very long time.

 

[ILENGINE]

There is a TH18 to Kohler command conversion available. It also requires a mounting kit available from Grasshopper as well as the new command engine.