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I just found out that I have a head gasket on one cylinder and stuck valves, with bent push rods on the other cylinder. The shop thinks by overheating, but it had plenty of oil, but the ethanol crap gas was old. They think that might have destroyed the engine. Does that sound right? I gather it is pretty easy to replace the gasket, but I'm not sure about he other cylinder problems, and the shop has not spent the time to look into it in detail. They recommend replacing the engine, or buying a new mower. I hate to buy a new mower, when this one has less than 100 hours and is less than 5 years old. I thought about just buying a rebuilt engine and replacing it myself. It looks like there are only 4 bolts and it would be almost trivial, but it will cost at least $1300, and a new mower is about $2700. My biggest problem is that if this was likely caused by the crap ethanol gas that we are forced to use, I might be better off spending the extra money to buy a decent, relatively low-time diesel zero turn. That would get better "mileage" and probably last at least 1500 to 2000 hours with relatively few problems, although I have never owned a diesel zero-turn. The other alternative is to replace the valves and head gasket myself. I have some experience with rebuilding aircraft engines. I suspect that would not be too hard, and probably not very expensive, but I don't know what would be involved.
Any thoughts or suggestions would be appreciated.

Most likely it's an AIR Cooled engine.... The flywheel has a fan that blows air over the cooling fins on the heads, if enough grass and debris gets built up it will hold heat and/or block air flow.

I did find a bit of a mouse nest, or something like that in one of the sets of cooling fins. Looking at the mower from the back, that would have been the right cylinder, I don't know which is officially the left and the right, but if that is the right, then it was the one with the stuck valves. I did, however, notice "dirt", which I suspect was exhaust, around that head valve cover. The other one looked like new.

The mouse it is what cooked that head. Without the engine info it is just a guessing game as to what parts you would but note it is repairable with new head, valves, valve train train components, and the associated gaskets.

Sounds to me like just swapping the motor might be a better idea, like the shop suggests. But, that still makes me wonder. If the mouse nest cooked the head, why was one head gasket blown (probably on that cylinder), but the valves stuck and the pushrods bent on the other cylinder? (Interestingly, the reason I had to rebuild one of my airplane engines was because the valve on the number 4 cylinder OF EACH engine got stuck and caused bent pushrods on the left engine, along with the engine swallowing one of the valves. The other engine just had a bent pushrod and was trivial to repair. Those problems were caused by switching from Aeroshell 15w-50 synthetic oil to Phillips 15w-50 synthetic oil when the FAA banned the Aeroshell oil. That problem took out whole fleets of aircraft that used the Lycoming IO-540 engine.)

If you can rebuild a Lycoming and it flies, literally , then a mower engine will not cause you any grief, other than by worrying about the massive clearances and lack thrust protection & bearings .
If it is a B & S then it will be dirt cheap as B &S parts are too cheap ( When you can get them )
Kohler parts are closer to proper price so Kohlers are a bit more expensive
Kawasaki parts are dearer still and can run to double what the equivalent B & S parts costs ..
Loncin parts ( Toro branded engnes ) can be a problem as Toro & MTD are playing things close to the chest forcing most to but branded parts from the dealers .

Usually the break down is parts 1/3 labour 2/3 so if your labour is involved it makes rebuilds very reasonable .
However no decisions can be made till a proper inspection of the engine is done .

The other problem is of course time and how close to the end of the mowing season you are.
Very soon surplus retailers like
SURPLUS CENTER
Small Engine Warehouse
small engine suppliers
Will start getting in this seasons leftover engines so prices will be quite low for a while

I don’t like swapping engines because I very seldom know the actual history of the replacement engines. If you would provide us with the model and serial numbers for the engine, we would be able to give you a better answer as to how each of us would proceed.

Kohler 7000, 22hp autochoke? Toro put this engine in the SS4225 for a handful of years including 2015. Just a guess but being in the Kohler sub-forum it only makes sense.

I don't know the serial number because it is still in the shop. But, it is a Kohler KT725-3031 for a Toro zero-turn 42".

It is the SS4225 Toro.

That series of Kohler was basically a good engine, so I would take a serious look at rebuilding, depending on what parts you will need and their cost. This manual will help you decide if you think you can do the work yourself. I would price out the parts you figure you need and add $100, in case you forget something. Might mean a tear down before deciding. http://resources.kohler.com/power/k...45.1658754340.1601335970-986432130.1601335970

The only issue is the labor. I just went through this with my CV15S when I considered having the valve work done. A head gasket job is $20-50 in parts but $360 in labor. The extent of the damage described sounds like minimum 6 billable hours plus parts which will near $800.

With the KT-725 engine, can you easily change the head gasket and push rods without removing the engine? I assume that is a pretty easy repair, especially if you don't have to remove the engine. I assume you need to remove the muffler. How hard or easy is that?

If I am going to repair, I will do it myself. Also, if I have to replace with a new (rebuilt) motor, I would do that myself. That appears to be almost trivial since I think there are only 4 bolts mounting the motor on the mower. I think I can get the motor, myself, for about $1300. The shop wants almost $1600 for the motor and about 4 hours of labor.

Scrubcadet10 said:

Most likely it's an AIR Cooled engine.... The flywheel has a fan that blows air over the cooling fins on the heads, if enough grass and debris gets built up it will hold heat and/or block air flow.

Click to expand...

Think I've heard of this before.

slomo

slomo said:

Think I've heard of this before.

slomo

Click to expand...

Funny how a 10 minute yearly cleaning procedure can later cost thousands of dollars.

slomo