are you applying the choke while trying to start the warm engine? If so, don't. Also try a new spark plug.. and check under the engine sheet metal to be clean and free of mice nests, etc. (overheating). and always run/work engine at WOT.

If still a prob, post back with what you did and updated problem description.

Uh........this engine IS NOT a Vee twin..............it is an OPPOSED twin, aka "boxer engine".
I don't know whether you are using the choke to start when the engine is hot, or not, but here is what I sometimes have to do on my opposed twin (baby brother to yours) when trying a hot or warm restart.
I move the throttle to wide open. Then I place one hand on the choke knob and the other hand on the key switch. Without operating the choke, I turn the key to start. If the engine does not start up after 1 second of cranking, I pull out the choke fully and immediately push it back down. This always gets it started. Before I tried this, I cranked for maybe 10 seconds or so before the engine would finally stumble back to running.
Most of the time if I have just shut off the engine for a couple of minutes, it restarts without having to use the brief application of choke.
But if the engine has been shut down for 5 minutes or so, it wants you to choke it.
So, I don't know if this will improve things for yours or not.

It is definitely running hot. The starting techique works. I will remove the shroud and clean. Thank you both for your imput. gw

I also use the starting technique mentioned by Mownie. This was a great engine and will last many years if it receives quality maintenance. Grass tends to collect in the cooling fin area. If overheating occurs, chances are the valve seats will loosen up. The top blower cover and the sheetmetal baffles over the cylinder heads and around the cylinders should be removed every couple of years for cleaning. I seal off the carburetor and places where water should not be introduced. The purple cleaner from Auto Zone works very well. Pressure washing takes care of the dirt.

They have a aluminum fan You can mount to the outside of the engine. Cannot remember what they call it but it scoops air into the other flywheel fan to make it run even cooler on hot days. They even have a fan screen that mounts over that one. It fits many engines. I seen the very same one on a Kohler and a Briggs opposed. It might even fit the Onan opposed too.