Kohler Command Valve stem seals

monster318 · Aug 23, 2015

Hello,
I have acquired a mid 90s Scag Super Z from a co-worker off a barter trade, at the time all he told me was it had internal engine problems and dealer told it him it would be around $800 to fix. I got it, brought it home, put fresh gas, oil, a battery and new spark plugs in it, and it fired right up. I mowed about 4 times before checking oil again and it was empty! none on the dip stick...refilled it and mowed several more times over the period of two months with it, ran out of oil again. It all of a sudden started misfiring on one cylinder. I pulled the plugs back out and Cylinder #1 was severely oil fouled. Ok now I have an explanation as to where all this oil was going. After some internet research I read a few forums of guys with these motors saying the valve guides like to crack and allow it it burn oil. I ripped the motor out of it, pulled cylinder head off and found no valve seal on exhaust cylinder and a lot of discoloring around that valve internally around the valve spring, almost like it was having blow through when the exhaust valve opened. Now from any and all knowledge I have ever had about motors, all motors had valve stem seals on both valves intake and exhaust..So immediately I think I found my problem. I order a Valve train kit, and valve stem seal kit from Kohler (which by the way came with two valve stem seals, so I put one on each valve). Was putting it back together tonight and had just finished up cylinder one side and decided to pull cylinder two valve cover off, and low and behold, no valve stem seal on that exhaust valve either and had same discoloring around valve spring.

So now I am really stumped and I turned to my Kohler Service Manual, It says directly in the service book that only Intake valves should have seals on them. So whats sealing the exhaust valve from having oil run down into the combustion chamber? This is also making me wonder if this is the real problem why I am burning oil.

its a Kohler Command 22HP Model CV22S-67509

Tomtint · Aug 23, 2015

I don't have anything to add to your dilemma. I can say, I will never own anything with a Kohler in it ever again. They are ticking time bombs .02

Helitech · Aug 23, 2015

That's normal on a Kohler. You may have badly worn valve guides as well. If that is the case you should replace the heads and valves.

monster318 · Aug 23, 2015

Would it hurt any to have valve seals on both Valves?

Helitech · Aug 23, 2015

Nope, will not hurt a thing. Owned a small engine shop for 10 years.

Jim Thompson · Aug 23, 2015

There would be no benefit to having a seal on the exhaust valve. No Kohler command engines that I've had apart had one from the factory. Only seal is on intake valve because you have a vacuum when it opens, whereas on the exhaust side you have pressure.
I would take a look at your head gasket. Very common problem on command twins. Check the area where the opening for the push rods pass through the head, can create high crank pressure and allow oil/ fumes to enter the combustion chamber on intake stroke.

slow84ta · Aug 24, 2015

I would go ahead and replace the entire head

RandyT · Aug 24, 2015

Just remember when you order the head it doesn't come with anything other than an empty head. Will need to order the head hardware kit, and the head gasket kit X2. Just pulled a CH22 out of a bush hog mower over the weekend. Part of the exhaust valve is missing on the number 1 cylinder, and signs of burning hardening on the number 2 cylinder exhaust valve.

chuckpen · Sep 10, 2017

A follow-up question for help.

I have a JD L130 with the Kohler Command 23 in it. This tractor sat for a number of years, never being used. Got it running good with a few parts but noticed a little blue when first starting but was livable.

This fall she started smoking more and now smokes even when running. Still runs fine.

So I was hoping for some wisdom before tearing apart so I can order everything I need before I decide to tear off the top end.

1. Just seals?
2. pull head and do gaskets
3. replace entire topend, new head, valves, seals, rockers and such?

tractor has less than 200 hours on it.

thoughts?
thanks everyone

tomplum · Sep 10, 2017

IF you certain that there is no fuel getting into the oil and have a belief that you are starting to burn oil, it would be likely that you have the beginning of a head gasket failure on this one. These tend to start smoking more once you start working them. Oil will blacken quicker, deposits build on the spark plugs. Since this engine was made, the head gaskets have been redesigned.

chuckpen · Sep 10, 2017

thanks. I'll order up the kits and see where it goes.

Stimw · Sep 10, 2017

Exhaust valves don't need seals because the exhaust chamber is under pressure when running.
Intake chamber is under a vacuum when running and can pull oil past the valve stem.

Need to check crank case vent, some have simple check valve that might be not working properly pressurizing crankcase forcing oil past rings.

RandyT · Sep 10, 2017

Check the breather reed valve in the head for cracks or warpage. they have been known to do both on the the Command engines. If looking at the carb end of the engine it should be located in the head on your left. Normally will have a breather assembly mounted above the valve cover.

chuckpen · Sep 10, 2017

Bit of an update:
Right side breather is clear. I do smell gas in the oil.

tomplum · Sep 11, 2017

The plot thins. Sounds likely there is a carb issue then. Especially as it has been sitting. Can you confirm extra fuel is entering the engine with the air filter off? Float valve, accelerator pump if equipped are better guesses. Fuel pumps can also leak into the crankcase, check via the pulse line. Fuel will enter the crankcase should only 1 cylinder be running as well.
In regards to the breather system. The reeds are in the block behind the head. On occasion one will be bad. The breather itself is maze below the carb on the front of the block. That seal has been updated ~ 4 times since the engine was built for leakage. The canister on the valve cover is a separator for the breather system.

chuckpen · Sep 12, 2017

Status update:

Ordered a new fuel pump, head gasket kits and valve seals. I have not tested vacuum on the crankcase as of yet to test the breather but that will be done before tear-down. Hopefully I'm not missing anything on my evaluation with all the help provided by everyone. Found the best pricing on eBay from a Kohler authorized reseller. $22 for head kit, about $6 for valve seals, free shipping, no tax. Ordered the fuel pump off Amazon to get it quick as I think ethanol probably toasted the fuel pump by sitting for those years soaking in gas. A guess but a 13 year old fuel pump cant be that good.

tomplum · Sep 13, 2017

So hopefully you read out of this discussion that you may not need to pull the cylinder heads at this time. The thinning of the oil from the fuel will cause excess smoking and the cause of such needs to be determined.

chuckpen · Mar 21, 2018

Well, yes, I was lazy this winter but Spring has arrived and now I need my tractor. I have an update on my oil burning / gas in oil problem with my Kohler Command 23. First thanks for all the guidance on this type of issue.

As I mentioned before, I had ordered a fuel pump, 2 head gasket kits and 2 intake valve seals.

After pulling the spark plugs all became clear, yes I know, why not do that before ordering parts. I will keep learning.

Anyway, left side plug was oil fouled and doubt it would even spark. Other side was perfect color, so pulled that one head and found oil/gas in the cylinder. Pretty surprised to see that. The head gasket looked fine, the valve seal looked "ok" and the valve seats seemed fine by testing with liquid carb cleaner and no leaks / seeping going past the valves. Cylinder walls still showed factory cross-hatching and looked fine. The head gasket also looked ok, so I was scratching my head thinking I was missing something. Also pulled apart the carb to clean and found the fuel shutoff solenoid was stuck. long story short; cleaned the carb and put back together, passed the head over a flat stone with some abrasive to clean, smooth up check for flatness. Replaced the intake valve seal, new head gasket with new washers and nuts, cleaned up the e3 plug and put it back together. Well, that has seemed to fix everything. Plug burn looks good, tractor was used for 4 hours after finishing up the rebuild and no smoking / oil burning to date. thanks again all!

So my assessment is:
bad head gasket or valve seal caused severe fouling in one cylinder.
gasoline went unburned and was able to find a way down to the crankcase oil.
condition of oil deteriorated to point where I started to burn the thinned oil.