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This guide is showing how to repair a leak at the RTV sealed closure plate on horizontal Kohler command engines. It specifically shows the repair on a 2001 Simplicity Legacy with a CH20 Kohler Command engine, but the principles will be similar for other tractors with similar engines.

I started having a fairly significant oil leak from my engine after I fixed a blown head gasket. I had a hard time finding the source of the leak as it appeared to just seep out from under the engine. I put in some UV dye for oil and was able to see oil seep out from around the closure plate. When I investigated further I found that several of the closure plate bolts were very loose and the seal was compromised.
As best I could figure out the only correct way to repair this is to remove the closure plate, clean the old RTV sealant off and put new stuff on. I was pretty scared of opening up the engine, but armed with Kohler repair manual I ventured into it.

Here is my description of it with lots of pictures showing the work. To my great relief I can tell that the engine is running great and also no longer have any oil leaks.

The first step is to remove the spark plug wires and the negative connection to the battery.

Remove the two bolts and hooks holding the hood and remove the hood

Then remove the PTO tension spring - it helps to have a real spring puller. But in a pinch a piece of wire will work too.

Remove the PTO belts. Remember to mark them first so they can go back on the same way.

Remove the drive shaft. This is kind of awkward to get to, but it is possible.
It really helps to have a hex key socket for the wrench (in this case 6 mm). The screw driver is for holding the drive shaft so it doesn't rotate when you try to loosen the screws.

First you have to remove the screen

Then remove the 4 bolts holding the drive shaft. You could move the engine forward before you remove these, but I think it was easier to take them out so to not disconnect the drive shaft from the hydro.

Prevent the drive shaft from rotate by inserting a long screwdriver through the yoke. Be careful not to damage the grease zerk

Use a breaker bar or an extender on a ratchet to break the crankshaft bolt loose.
I am using a piece of steel pipe over a ratchet.

Remove the fan (this is unique to Simplicity Legacy)
This will give access to the PTO clutch.

Disconnect the PTO clutch electrical connection

And slide off the PTO clutch.
Be careful not to loose the key if it is loose in the keyway

My key was stuck very good in the keyway and I had a hard time getting it out.
I ended up pushing it forward by wedging a screwdriver between the engine and the brass spacer that was on the crank shaft.

Time to remove the muffler. Start by taking off the bolts on each cylinder for exhaust.

Then remove the center bolt holding the muffler

You can now set the muffler aside. Your engine should look something like this now.

Before we can remove the engine we need to disconnect everything that connects it to the tractor. First is the fuel line.

Then the electrical connection for the starter

And the ground strap

Unplug the electrical plug on the engine

Disconnect the throttle and choke cable. If you mark them first it will be easier to re-install them in the correct position again.

This engine has the extra oil cooler on it. The oil filter and cooler adapter plate is on the closure plate while the cooler itself is on the shroud. So we need to disconnect them in order to be able to remove the closure plate.
First remove the oil filter

Then remove the bolt holding the adapter plate

Remove the 4 bolts holding the engine to the tractor. You may note the oil running down the front axle. The UV dye is giving it this abnormal color.

And lift the engine out of the tractor. I set it on a work dolly so it is easier to move around. Make sure you have it lifted up if you leave the oil drain in as I did here.

So far so good. I have tried this before, but now I venture into unknown territory.

Per the instructions you lay the engine on the flywheel side and remove the 10 bolts holding the closure plate. One was plated out of the 10 – it is not special or different. I think it is just a way Kohler checks to see if the engine has been opened in case of warranty claims. Then use a ½” breaker bar to break the seal.

In my case the seal was already broken so it was pretty easy. There are 3 tabs you can use for breaking. Since I did not remove the carb the top one is tough to get at. However it was not needed in my case. Slide the closure plate off the crankshaft and marvel at the innards of the engine.
This is what the inside of the closure plate looks like. There is the oil pump and parts for the governor.

Here is the engine side. You can see the camshaft and crankshaft. What you cannot see much of is the RTV sealant. I guess they went really light on this one which is probably why it leaked.

Most of the sealant that was there could be removed by hand by just putting your nail into it. The rest I removed with some paint thinner. Here is the closure plate cleaned

And the engine side cleaned

Here is the RTV sealant I will be using. The Kohler manual calls for Loctite 5900, but that is pretty much impossible to get a hold of for a consumer. I did find it available in 5 gallon buckets, but I can see no need for that amount
Permatex tech support crossed it to this product. This is an extremely fast setting RTV sealant. Sets in about 5 min and according to instructions engine is ready for service as soon as it is assembled.

Kohler manual calls for a 1/16” bead. However the can already came with an approx. 1/8” hole in the nozzle. So I went for it. Make sure you have the collar inserted into the oil passage so you do not get any sealant in there. The sealant goes on both sides of the collar as shown.

Now you have 5 min to assemble it, so I did not take any pictures from that.
However you may need to rotate the camshaft to get the gears to mesh with the oil pump and the governor. You also need the collars for the oil passages to line up.
I greased the crankshaft first to make sure I would not tear the oil seal.
I then used a rubber mallet to help me get everything together again. Make sure you follow the correct torque sequence from the manual. It is relatively light torque needed on these bolts.
Here it is all put together again.

Remember to slide on the brass collar before you put the key in the keyway.

Make sure you orient the keyway in the PTO clutch with the key before you try to slide it on.

Here is the clutch installed

And the fan. I am not tightening it to the correct torque until the engine is back in the tractor – that way I can lock the drive shaft when I tighten the bolt. Make sure you put the fan on the correct way – you want it to blow the air away from the engine.

Install the muffler with the exhaust bolts and the main bolt

Now you can lift the engine into the tractor

Now connect all the electrical connections, connect the fuel line, the throttle and choke and install the engine mount bolts.
I am not showing picture off all these items as it is the reverse of disassembly.

Here is the engine all back in the tractor.
No oil leaks – fantastic.

It was a relatively long project for a rookie like me – around 5 hours total time spent. But the result is worth it.
Total cost was approx $ 20 for the RTV sealant and paint thinner.
Compare that to $ 300+ for having it done at a shop.

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