Reed valves are in the block behind the cylinder head. The breather is the cover plate between the heads.Likely a cylinder head gasket failure. The manual is there. Hit the Command twin icon.

Here is a link that might be useful: Kohler

Compression 140 (no1)and 150 (no2)PSI. Leakdown leads me to believe slight leak into carb on #1. Very slight. Gasket or valve? Would that cause crankcase pressure?

A leaking valve isn't going to bleed air into the crankcase.
It'll leak to the carb or exhaust, depending on which valve.

I doubt you have a bad head gasket with those compression readings.
I'd guess you have a defective reed valve in the breather.

How to determine which side is bad? Looks to me like you have to pull the head to get at?

A Reed valve is part of the breather. It's basically a "flapper".
Which "side" does not apply.

You didn't say if you had an oil consumption issue. On these engines, the front cover between the heads is the breather cover. There aren't any serviceable parts behind other than the gasket and cover. The gasket has in history been revised at least three times to a printed type. You can get the whole cover w/ gasket to be sure if you wanted to try quick and easy. Personally, I've only seen external leaks on these. Reeds can break, but rarely do. If you have a spark plug that is showing much more carbon deposits than the other- that would be a real likely candidate for a gasket failure. If it comes apart, it is advisable to do both sides.

The breather cover is off now and the gasket appeared to be all good. Behind it very clean. As for oil consumption... I got the mower from a guy in a swap. All he told me was it shoots oil out. When I started it would not run at all cleaned up got rid of old gas fixed electrical problem why it would not start - bad brake switch. And it fired right up. When I shut down I decided to check oil level. The cap like blew into my hand. Oil level was not on the stick. Added 1.5 qts to get to low level. Ran again - no smoke Shot oil out plastic plug near starter. Pulled breather - (looking for reed) found them inside valve cover later. Thats how we are here.

So you have reed valves lying in the valve cover? Then you know what to do. I would also do both dipstick seals when you order parts.

I'll get the heads off today and post what I find. Thanks.

Confused. Found both head gaskets to be good both breathers good. Valves look decent. Cylinder walls show cross hatch pattern. Guess I'll get some gaskets and new reeds and re-assmeble. Any other ideas?

It really doesn't take much gasket loss between the cylinder and oil galley to build pressure. I had a Courage twin that even after adjusting oil level and servicing the breather I kept going and did gaskets that showed nothing definitive to correct a smoke issue. there was a bulletin on these breathers. The breather on a Courage is different though. The only bulletin I've seen on Command twins were some gasket changes and some early special policy type things. I'm confused about what you found in the valve cover though if it wasn't the reeds. Was there carbon build in either of the cylinders? On the parts list, add the breather cover kit, the dip stick seals plus change the oil (10w30 or SAE 30 if + 50 degrees) and Kohler oil filter. You also want to be sure this thing can breath well through the air filter and that there is not an exhaust restriction- like from a custom deal or broken muffler baffle etc.

I decided to order a complete gasket kit and the reeds. The Hour meter shows 200 got to believe it has more than that. Hour meter works but is on whenever key switch is on, not when engine is running. So if key got left on Hour meter could be 10200. Or meter got switched out some where along the way. Got the engine out of the mower now will begin tear down and clean-up. On the side it has a plastic drain assy. This is what blows open. I will change to steel pipe with cap to make it easier to change oil. Dipstick appears to not seal too great so I'll make sure it fits better when assembled. Internals very clean with only minor carbon on top of pistons. Both plugs Brownish black Not too sooty.

Forgot to add. I put a rag on each muffler pipe when I removed it and could blow through it easily.

So while it is off, is your plan to look at the rings? Wouldn't it be great if your entire issue was a worn out drain and dipstick seal! Did you ever identify what you found in the valve cover?

Motor is all apart on the bench. Findings: Rings lined up within 1/2" both cylinders. One oil pan bolt completely white like antifreeze burn. After looking at the pan bolt holes I notice that one of them intersects with a head bolt hole. Overall everything looks good. Will assemble with all new seals and gaskets.

Cool. Keep us posted.