04 Simplicity Prestige: Kohler Questions, possible headg

Hello all. Long time lurker, just signed up so first post... I do apologize if posting in wrong place.

I'm moving to a property with 3+ mowable acres. My trusty 4211 is a little undersized I think...I just picked up an 04 Prestige from original owner w/54" deck. It seemingly has been maintained with 617hrs. on the clock. Previous owner stated it recently started burning oil and smoking, mostly at startup. (It seems to be burning some oil excessively all the time) He upgraded to a larger mower and dumped it on me for $1200. Included was a good condition snowblower that i need...

Anyways it has a 23HP Kohler Command "HO". Worst case scenario I assumed oil control rings worn out. Now I suspect a likely blown head gasket into oil galley? I wish i could easily post a video but machine does smoke on startup and breather hose from valve cover seems to have excessive pressure with a steady oil mist when running. I pulled spark plugs and the right side had tons of buildup, both look slightly oil fouled. Machine starts easy and seems to run well. I have not yet done a compression test or leakdown. Does this seem on par with a blown headgasket?

IF head gasket blown? Will the upgraded Kohler head gasket kit with ring around the cylinder part from 25-27hp machines work with this old 23HP????

No. The head gasket on a 25-27 hp will not fit a 23 hp engine.
You need the one that fits the 18-23 hp engines.

A few years ago Kohler had problems with larger engines in the 21-27 hp range blowing head gaskets. They came from the factory with weak head bolts that would stretch beyond specs and blow head gaskets. For awhile Kohler would replace the head gaskets for free and included a set of better quality head bolts in a kit that cured the problem. I daught they are still offering the kits for free with the amount of time that has passed.

Be sure to get a kit that includes the head bolts even if it cost a little more than just buying the gaskets alone. For if you don't. You will have the same problem again.

Thanks Mule Meat, I appreciate the reply.

Another possibility to look for is a bad crank seal. It can cause an over-pressurization of the
crankcase and oil out the breather yet still run good.

Thanks Blackhole. I'm new to twin Kohlers but my understanding is that blown headgasket(s) are pretty common with these? Will check for crank seal leak. Hopefully I don't have to pull engine, downtime wise... Just in case, I ordered one head gasket kit from Kohler with the part number I found. I'm assuming that the heads use studs rather than bolts as it only comes with head nuts. If bolts, I will replace. Will check head or heads for flatness. Extremely busy with moving but will do a comp check and leakdown when I get time, possibly camera inspection.

I'm planning on keeping oil in it and using the mower as-is temporarily as I need to mow a bunch of long grass. I suppose I'm risking crank seal damage by doing so, assuming not leaking yet.

Well, of all things discussed, pulling it apart and inspecting the head gaskets would be my guess. And easier and a lot cheaper than a
ring job. Assuming the customer gave the engine regular oil changes and used a quality oil, the rings should be o.k. (I have seen some of
those Kohler Commands with over 2,000 hours on them.)

I am not familiar with the 'bad crank seal' causing an engine to smoke. It would seem to me that a bad crank seal would relieve the excess
pressure in the crankcase that would otherwise push oil through the crankcase breather and into the carburetor throat, where it can burn
along with the fuel. It probably should be leaking oil at that seal too.

One thing that blows a lot of those head gaskets is closing the throttle before switching the engine off. You want to keep the air
velocity up in the muffler so that when you kill the spark the pistons will push the unburnt fuel all the way through the muffler before
it has a chance to ignite. A backfire in the muffler is an uncontrolled explosion and if the exhaust valve is open it can damage the head
gasket.

Makes perfect sense. Thanks T.R.K.

My 16hp Onan had a bad crank seal and smoked. Great compression and ran fine. The bad seal allowed the engine to suck too much air into the crankcase and spit oil out the breather tube into the carb. I replaced the seal and the engine was running fine with no oil use for several years until I sold the machine (Case 446). When our Kohlers at work had bad head caskets (several), they didn't run great. Just my experience, your mileage may very.

I just wanted to follow up here. I finally found some time to tear this thing down and confirmed a blown head gasket (right head) was allowing combustion pressure to enter crankcase oil passage. I was able to mow most of my newly acquired 3 acres with this unit. It did surprisingly always run well. Didn't really go through much oil. Crankcase pressure got so bad it blew a wide open hose off valve cover breather to intake. Called it quits at that point. Heavy oil deposits on valves and plug.

Unable to find updated gasket for 23hp. Resurfaced head and installed new gasket with copper coat. Going to do other side while its apart. New crankcase breather valve and related parts ordered.

Thanks for the help guys.