Toro Z-5000 oil leak

[Rusty1]

I have an 07 Toro Z-5000 with engine Kohler Courage 21 Model# SV610,and while mowing last week I notice smoke coming from the rear of the mower.Stopped the mower and checked the oil and it was a little below the add mark.I added oil then drove it back up to the garage,then noticed oil leaking on the driveway.I looked under(while engine was running)to see where it was coming from and could only see drips of oil at where the last jug fins end at the crankcase,but not where it was actually leaking from.
Is there a seal or gasket located where I've described the leak,or is it possible I have a cracked crankcase?
Any help greatly appreciated.

[Rivets]

I suspect that the oil is coming from a bad valve cover gasket. Trick I use to trace oil leaks. Clean and dry the entire suspected area. Use a fine powder to coat the suspected area, (baby, foot, flour, etc.). Run the unit and watch for an oil trail.

[reynoldston]

Being a Kohler courage engine the engine cases ten to crack. The last one I repaired I had welded and it is working out just fine. Yes find the leak frist as Rivets told you.

[Rusty1]

I suspect that the oil is coming from a bad valve cover gasket. Trick I use to trace oil leaks. Clean and dry the entire suspected area. Use a fine powder to coat the suspected area, (baby, foot, flour, etc.). Run the unit and watch for an oil trail.

Rivets,the valve cover gasket was just replaced this past March,and the valve cover is on the rear of the motor,it's very difficult to see where the leak is because it's underneath where the cylinder jug meets the crankcase.Where the leak is coming from is very difficult to see because of the plate the motor is mounted gives no room to see,and even using talc powder I still can't see where the leak originates,I can only see it dripping off the last cooling fin next to the crankcase.
I guess the only thing to do is pull the motor and look for cracks and maybe start the motor after mounting it to the workbench and check while it's running,because that's when it leaks.

reynoldston you may be right suspecting a crack in the crankcase,because it doesn't start leaking until the engine has been warmed up a few minutes,and the metal expands.

[reynoldston]

As I recall just 4 bolts and the plastic cover comes off the top of the engine. Once that is off just maybe you can see something without pulling the engine first. I wouldn't want to run the engine on the work bench for a number of reasons not that it can't be done. Its not that bad of a engine to work on other then the crankcase cover is on top of the engine. If you do have a crack they recommend a new short block. My customer didn't want to spend 1000 dollars to install a new engine so I had his crankcase welded by a welding shop and coated the inside of the crack with JB weld. So far its been working out good for him. Cost was 70 dollars at the weling shop and 6 dollars for the JB weld + new gaskets and seals.

[Rusty1]

Thanks very much for the help reynoldston and Rivets